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+// file : libbuild2/variable.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef LIBBUILD2_VARIABLE_HXX
+#define LIBBUILD2_VARIABLE_HXX
+
+#include <map>
+#include <set>
+#include <type_traits> // aligned_storage
+#include <unordered_map>
+
+#include <libbutl/prefix-map.mxx>
+#include <libbutl/multi-index.mxx> // map_key
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/target-type.hxx>
+
+#include <libbuild2/export.hxx>
+
+namespace build2
+{
+ // Some general variable infrastructure rules:
+ //
+ // 1. A variable can only be entered or typified during the load phase.
+ //
+ // 2. Any entity (module) that caches a variable value must make sure the
+ // variable has already been typified.
+ //
+ // 3. Any entity (module) that assigns a target-specific variable value
+ // during a phase other than load must make sure the variable has already
+ // been typified.
+
+ class value;
+ struct variable;
+ struct lookup;
+
+ struct value_type
+ {
+ const char* name; // Type name for diagnostics.
+ const size_t size; // Type size in value::data_ (only used for PODs).
+
+ // Base type, if any. We have very limited support for inheritance: a
+ // value can be cast to the base type. In particular, a derived/base value
+ // cannot be assigned to base/derived. If not NULL, then the cast function
+ // below is expected to return the base pointer if its second argument
+ // points to the base's value_type.
+ //
+ const value_type* base_type;
+
+ // Element type, if this is a vector.
+ //
+ const value_type* element_type;
+
+ // Destroy the value. If it is NULL, then the type is assumed to be POD
+ // with a trivial destructor.
+ //
+ void (*const dtor) (value&);
+
+ // Copy/move constructor and copy/move assignment for data_. If NULL, then
+ // assume the stored data is POD. If move is true then the second argument
+ // can be const_cast and moved from. copy_assign() is only called with
+ // non-NULL first argument.
+ //
+ void (*const copy_ctor) (value&, const value&, bool move);
+ void (*const copy_assign) (value&, const value&, bool move);
+
+ // While assign cannot be NULL, if append or prepend is NULL, then this
+ // means this type doesn't support this operation. Variable is optional
+ // and is provided only for diagnostics. Return true if the resulting
+ // value is not empty.
+ //
+ void (*const assign) (value&, names&&, const variable*);
+ void (*const append) (value&, names&&, const variable*);
+ void (*const prepend) (value&, names&&, const variable*);
+
+ // Reverse the value back to a vector of names. Storage can be used by the
+ // implementation if necessary. Cannot be NULL.
+ //
+ names_view (*const reverse) (const value&, names& storage);
+
+ // Cast value::data_ storage to value type so that the result can be
+ // static_cast to const T*. If it is NULL, then cast data_ directly. Note
+ // that this function is used for both const and non-const values.
+ //
+ const void* (*const cast) (const value&, const value_type*);
+
+ // If NULL, then the types are compared as PODs using memcmp().
+ //
+ int (*const compare) (const value&, const value&);
+
+ // If NULL, then the value is never empty.
+ //
+ bool (*const empty) (const value&);
+ };
+
+ // The order of the enumerators is arranged so that their integral values
+ // indicate whether one is more restrictive than the other.
+ //
+ enum class variable_visibility: uint8_t
+ {
+ // Note that the search for target type/pattern-specific terminates at
+ // the project boundary.
+ //
+ normal, // All outer scopes.
+ project, // This project (no outer projects).
+ scope, // This scope (no outer scopes).
+ target, // Target and target type/pattern-specific.
+ prereq // Prerequisite-specific.
+ };
+
+ // VC14 reports ambiguity but seems to work if we don't provide any.
+ //
+#if !defined(_MSC_VER) || _MSC_VER > 1900
+ inline bool
+ operator> (variable_visibility l, variable_visibility r)
+ {
+ return static_cast<uint8_t> (l) > static_cast<uint8_t> (r);
+ }
+
+ inline bool
+ operator>= (variable_visibility l, variable_visibility r)
+ {
+ return static_cast<uint8_t> (l) >= static_cast<uint8_t> (r);
+ }
+
+ inline bool
+ operator< (variable_visibility l, variable_visibility r)
+ {
+ return r > l;
+ }
+
+ inline bool
+ operator<= (variable_visibility l, variable_visibility r)
+ {
+ return r >= l;
+ }
+#endif
+
+ LIBBUILD2_SYMEXPORT ostream&
+ operator<< (ostream&, variable_visibility);
+
+ // variable
+ //
+ // The two variables are considered the same if they have the same name.
+ //
+ // Variables can be aliases of each other in which case they form a circular
+ // linked list (the aliases pointer for variable without any aliases points
+ // to the variable itself).
+ //
+ // If the variable is overridden on the command line, then override is the
+ // linked list of the special override variables. Their names are derived
+ // from the main variable name as <name>.<N>.{__override,__prefix,__suffix}
+ // and they are not entered into the var_pool. The override variables only
+ // vary in their names and visibility. Their aliases pointer is re-purposed
+ // to make the list doubly-linked with the first override's aliases pointer
+ // pointing to the last element (or itself).
+ //
+ // Note also that we don't propagate the variable type to override variables
+ // and we keep override values as untyped names. They get "typed" when they
+ // are applied.
+ //
+ // The overrides list is in the reverse order of the overrides appearing on
+ // the command line, which is important when deciding whether and in what
+ // order they apply (see find_override() for details).
+ //
+ // The <N> part in the override variable name is its position on the command
+ // line, which effectively means we will have as many variable names as
+ // there are overrides. This strange arrangement is here to support multiple
+ // overrides. For example:
+ //
+ // b config.cc.coptions=-O2 config.cc.coptions+=-g config.cc.coptions+=-Wall
+ //
+ // We cannot yet apply them to form a single value since this requires
+ // knowing their type. And there is no way to store multiple values of the
+ // same variable in any given variable_map. As a result, the best option
+ // appears to be to store them as multiple variables. While not very
+ // efficient, this shouldn't be a big deal since we don't expect to have
+ // many overrides.
+ //
+ // We use the "modify original, override on query" model. Because of that, a
+ // modified value does not necessarily represent the actual value so care
+ // must be taken to re-query after (direct) modification. And because of
+ // that, variables set by the C++ code are by default non-overridable.
+ //
+ // Initial processing including entering of global overrides happens in
+ // reset() before any other variables. Project wide overrides are entered in
+ // main(). Overriding happens in scope::find_override().
+ //
+ // NULL type and normal visibility are the defaults and can be overridden by
+ // "tighter" values.
+ //
+ struct variable
+ {
+ string name;
+ const variable* aliases; // Circular linked list.
+ const value_type* type; // If NULL, then not (yet) typed.
+ unique_ptr<const variable> overrides;
+ variable_visibility visibility;
+
+ // Return true if this variable is an alias of the specified variable.
+ //
+ bool
+ alias (const variable& var) const
+ {
+ const variable* v (aliases);
+ for (; v != &var && v != this; v = v->aliases) ;
+ return v == &var;
+ }
+
+ // Return the length of the original variable if this is an override,
+ // optionally of the specified kind (__override, __prefix, etc), and 0
+ // otherwise (so this function can be used as a predicate).
+ //
+ // @@ It would be nicer to return the original variable but there is no
+ // natural place to store such a "back" pointer. The overrides pointer
+ // in the last element could work but it is owning. So let's not
+ // complicate things for now seeing that there are only a few places
+ // where we need this.
+ //
+ size_t
+ override (const char* k = nullptr) const
+ {
+ size_t p (name.rfind ('.'));
+ if (p != string::npos)
+ {
+ auto cmp = [this, p] (const char* k)
+ {
+ return name.compare (p + 1, string::npos, k) == 0;
+ };
+
+ if (k != nullptr
+ ? (cmp (k))
+ : (cmp ("__override") || cmp ("__prefix") || cmp ("__suffix")))
+ {
+ // Skip .<N>.
+ //
+ p = name.rfind ('.', p - 1);
+ assert (p != string::npos && p != 0);
+ return p;
+ }
+ }
+
+ return 0;
+ }
+ };
+
+ inline bool
+ operator== (const variable& x, const variable& y) {return x.name == y.name;}
+
+ inline ostream&
+ operator<< (ostream& os, const variable& v) {return os << v.name;}
+
+ //
+ //
+ class LIBBUILD2_SYMEXPORT value
+ {
+ public:
+ // NULL means this value is not (yet) typed.
+ //
+ // Atomic access is used to implement on-first-access typification of
+ // values store in variable_map. Direct access as well as other functions
+ // that operate on values directly all use non-atomic access.
+ //
+ relaxed_atomic<const value_type*> type;
+
+ // True if there is no value.
+ //
+ bool null;
+
+ // Extra data that is associated with the value that can be used to store
+ // flags, etc. It is initialized to 0 and copied (but not assigned) from
+ // one value to another but is otherwise untouched (not even when the
+ // value is reset to NULL).
+ //
+ // Note: if deciding to use for something make sure it is not overlapping
+ // with an existing usage.
+ //
+ uint16_t extra;
+
+ explicit operator bool () const {return !null;}
+ bool operator== (nullptr_t) const {return null;}
+ bool operator!= (nullptr_t) const {return !null;}
+
+ // Check in a type-independent way if the value is empty. The value must
+ // not be NULL.
+ //
+ bool
+ empty () const;
+
+ // Creation. A default-initialzied value is NULL and can be reset back to
+ // NULL by assigning nullptr. Values can be copied and copy-assigned. Note
+ // that for assignment, the values' types should be the same or LHS should
+ // be untyped.
+ //
+ //
+ public:
+ ~value () {*this = nullptr;}
+
+ explicit
+ value (nullptr_t = nullptr): type (nullptr), null (true), extra (0) {}
+
+ explicit
+ value (const value_type* t): type (t), null (true), extra (0) {}
+
+ explicit
+ value (names); // Create untyped value.
+
+ explicit
+ value (optional<names>);
+
+ template <typename T>
+ explicit
+ value (T); // Create value of value_traits<T>::value_type type.
+
+ template <typename T>
+ explicit
+ value (optional<T>);
+
+ // Note: preserves type.
+ //
+ value&
+ operator= (nullptr_t) {if (!null) reset (); return *this;}
+
+ value (value&&);
+ explicit value (const value&);
+ value& operator= (value&&);
+ value& operator= (const value&);
+ value& operator= (reference_wrapper<value>);
+ value& operator= (reference_wrapper<const value>);
+
+ // Assign/Append/Prepend.
+ //
+ public:
+ // Assign/append a typed value. For assign, LHS should be either of the
+ // same type or untyped. For append, LHS should be either of the same type
+ // or untyped and NULL.
+ //
+ template <typename T> value& operator= (T);
+ template <typename T> value& operator+= (T);
+
+ template <typename T> value& operator= (T* v) {
+ return v != nullptr ? *this = *v : *this = nullptr;}
+
+ template <typename T> value& operator+= (T* v) {
+ return v != nullptr ? *this += *v : *this;}
+
+ value& operator= (const char* v) {return *this = string (v);}
+ value& operator+= (const char* v) {return *this += string (v);}
+
+ // Assign/append/prepend raw data. Variable is optional and is only used
+ // for diagnostics.
+ //
+ void assign (names&&, const variable*);
+ void assign (name&&, const variable*); // Shortcut for single name.
+ void append (names&&, const variable*);
+ void prepend (names&&, const variable*);
+
+
+ // Implementation details, don't use directly except in representation
+ // type implementations.
+ //
+ public:
+ // Fast, unchecked cast of data_ to T.
+ //
+ template <typename T> T& as () & {return reinterpret_cast<T&> (data_);}
+ template <typename T> T&& as () && {return move (as<T> ());}
+ template <typename T> const T& as () const& {
+ return reinterpret_cast<const T&> (data_);}
+
+ public:
+ // The maximum size we can store directly is sufficient for the most
+ // commonly used types (string, vector, map) on all the platforms that we
+ // support (each type should static assert this in its value_traits
+ // specialization below). Types that don't fit will have to be handled
+ // with an extra dynamic allocation.
+ //
+ static constexpr size_t size_ = sizeof (name_pair);
+ std::aligned_storage<size_>::type data_;
+
+ // Make sure we have sufficient storage for untyped values.
+ //
+ static_assert (sizeof (names) <= size_, "insufficient space");
+
+ private:
+ void
+ reset ();
+ };
+
+ // This is what we call a "value pack"; it can be created by the eval
+ // context and passed as arguments to functions. Usually we will have just
+ // one value.
+ //
+ using values = small_vector<value, 1>;
+
+ // The values should be of the same type (or both be untyped) except NULL
+ // values can also be untyped. NULL values compare equal and a NULL value
+ // is always less than a non-NULL.
+ //
+ LIBBUILD2_SYMEXPORT bool operator== (const value&, const value&);
+ bool operator!= (const value&, const value&);
+ LIBBUILD2_SYMEXPORT bool operator< (const value&, const value&);
+ bool operator<= (const value&, const value&);
+ LIBBUILD2_SYMEXPORT bool operator> (const value&, const value&);
+ bool operator>= (const value&, const value&);
+
+ // Value cast. The first three expect the value to be not NULL. The cast
+ // from lookup expects the value to also be defined.
+ //
+ // Note that a cast to names expects the value to be untyped while a cast
+ // to vector<name> -- typed.
+ //
+ // Why are these non-members? The cast is easier on the eyes and is also
+ // consistent with the cast operators. The other two are for symmetry.
+ //
+ template <typename T> T& cast (value&);
+ template <typename T> T&& cast (value&&);
+ template <typename T> const T& cast (const value&);
+ template <typename T> const T& cast (const lookup&);
+
+ // As above but returns NULL if the value is NULL (or not defined, in
+ // case of lookup).
+ //
+ template <typename T> T* cast_null (value&);
+ template <typename T> const T* cast_null (const value&);
+ template <typename T> const T* cast_null (const lookup&);
+
+ // As above but returns empty value if the value is NULL (or not defined, in
+ // case of lookup).
+ //
+ template <typename T> const T& cast_empty (const value&);
+ template <typename T> const T& cast_empty (const lookup&);
+
+ // As above but returns the specified default if the value is NULL (or not
+ // defined, in case of lookup). Note that the return is by value, not by
+ // reference.
+ //
+ template <typename T> T cast_default (const value&, const T&);
+ template <typename T> T cast_default (const lookup&, const T&);
+
+ // As above but returns false/true if the value is NULL (or not defined,
+ // in case of lookup). Note that the template argument is only for
+ // documentation and should be bool (or semantically compatible).
+ //
+ template <typename T> T cast_false (const value&);
+ template <typename T> T cast_false (const lookup&);
+
+ template <typename T> T cast_true (const value&);
+ template <typename T> T cast_true (const lookup&);
+
+
+ // Assign value type to the value. The variable is optional and is only used
+ // for diagnostics.
+ //
+ template <typename T>
+ void typify (value&, const variable*);
+ void typify (value&, const value_type&, const variable*);
+
+ LIBBUILD2_SYMEXPORT void
+ typify_atomic (value&, const value_type&, const variable*);
+
+ // Remove value type from the value reversing it to names. This is similar
+ // to reverse() below except that it modifies the value itself.
+ //
+ LIBBUILD2_SYMEXPORT void untypify (value&);
+
+ // Reverse the value back to names. The value should not be NULL and storage
+ // should be empty.
+ //
+ vector_view<const name>
+ reverse (const value&, names& storage);
+
+ vector_view<name>
+ reverse (value&, names& storage);
+
+ // lookup
+ //
+ // A variable can be undefined, NULL, or contain a (potentially empty)
+ // value.
+ //
+ class variable_map;
+
+ struct lookup
+ {
+ using value_type = build2::value;
+
+ // If vars is not NULL, then value is variable_map::value_data.
+ //
+ const value_type* value; // NULL if undefined.
+ const variable* var; // Storage variable.
+ const variable_map* vars; // Storage map.
+
+ bool
+ defined () const {return value != nullptr;}
+
+ // Note: returns true if defined and not NULL.
+ //
+ explicit operator bool () const {return defined () && !value->null;}
+
+ const value_type& operator* () const {return *value;}
+ const value_type* operator-> () const {return value;}
+
+ // Return true if this value belongs to the specified scope or target.
+ // Note that it can also be a target type/pattern-specific value in which
+ // case it won't belong to either unless we pass true as a second argument
+ // to consider it belonging to a scope (note that this test is expensive).
+ //
+ template <typename T>
+ bool
+ belongs (const T& x) const {return vars == &x.vars;}
+
+ template <typename T>
+ bool
+ belongs (const T& x, bool target_type_pattern) const;
+
+ lookup (): value (nullptr), var (nullptr), vars (nullptr) {}
+
+ template <typename T>
+ lookup (const value_type& v, const variable& r, const T& x)
+ : lookup (&v, &r, &x.vars) {}
+
+ lookup (const value_type& v, const variable& r, const variable_map& m)
+ : lookup (&v, &r, &m) {}
+
+ lookup (const value_type* v, const variable* r, const variable_map* m)
+ : value (v),
+ var (v != nullptr ? r : nullptr),
+ vars (v != nullptr ? m : nullptr) {}
+ };
+
+ // Two lookups are equal if they point to the same variable.
+ //
+ inline bool
+ operator== (const lookup& x, const lookup& y)
+ {
+ bool r (x.value == y.value);
+ assert (!r || x.vars == y.vars);
+ return r;
+ }
+
+ inline bool
+ operator!= (const lookup& x, const lookup& y) {return !(x == y);}
+
+
+ // Representation types.
+ //
+ // Potential optimizations:
+ //
+ // - Split value::operator=/+=() into const T and T&&, also overload
+ // value_traits functions that they call.
+ //
+ // - Specialization for vector<names> (if used and becomes critical).
+ //
+ template <typename T, typename E>
+ struct value_traits_specialization; // enable_if'able specialization support.
+
+ template <typename T>
+ struct value_traits: value_traits_specialization <T, void> {};
+ // {
+ // static_assert (sizeof (T) <= value::size_, "insufficient space");
+ //
+ // // Convert name to T. If rhs is not NULL, then it is the second half
+ // // of a pair. Only needs to be provided by simple types. Throw
+ // // invalid_argument (with a message) if the name is not a valid
+ // // representation of value (in which case the name should remain
+ // // unchanged for diagnostics).
+ // //
+ // static T convert (name&&, name* rhs);
+ //
+ // // Assign/append/prepend T to value which is already of type T but can
+ // // be NULL.
+ // //
+ // static void assign (value&, T&&);
+ // static void append (value&, T&&);
+ // static void prepend (value&, T&&);
+ //
+ // // Reverse a value back to name. Only needs to be provided by simple
+ // // types.
+ // //
+ // static name reverse (const T&);
+ //
+ // // Compare two values. Only needs to be provided by simple types.
+ // //
+ // static int compare (const T&, const T&);
+ //
+ // // Return true if the value is empty.
+ // //
+ // static bool empty (const T&);
+ //
+ // // True if can be constructed from empty names as T().
+ // //
+ // static const bool empty_value = true;
+ //
+ // static const T empty_instance;
+ //
+ // // For simple types (those that can be used as elements of containers),
+ // // type_name must be constexpr in order to sidestep the static init
+ // // order issue (in fact, that's the only reason we have it both here
+ // // and in value_type.name -- value_type cannot be constexpr because
+ // // of pointers to function template instantiations).
+ // //
+ // static const char* const type_name;
+ // static const build2::value_type value_type;
+ // };
+
+ // Convert name to a simple value. Throw invalid_argument (with a message)
+ // if the name is not a valid representation of value (in which case the
+ // name remains unchanged for diagnostics). The second version is called for
+ // a pair.
+ //
+ template <typename T> T convert (name&&);
+ template <typename T> T convert (name&&, name&&);
+
+ // As above but can also be called for container types. Note that in this
+ // case (container) if invalid_argument is thrown, the names are not
+ // guaranteed to be unchanged.
+ //
+ //template <typename T> T convert (names&&); (declaration causes ambiguity)
+
+ // Convert value to T. If value is already of type T, then simply cast it.
+ // Otherwise call convert(names) above.
+ //
+ template <typename T> T convert (value&&);
+
+ // Default implementations of the dtor/copy_ctor/copy_assing callbacks for
+ // types that are stored directly in value::data_ and the provide all the
+ // necessary functions (copy/move ctor and assignment operator).
+ //
+ template <typename T>
+ static void
+ default_dtor (value&);
+
+ template <typename T>
+ static void
+ default_copy_ctor (value&, const value&, bool);
+
+ template <typename T>
+ static void
+ default_copy_assign (value&, const value&, bool);
+
+ // Default implementations of the empty callback that calls
+ // value_traits<T>::empty().
+ //
+ template <typename T>
+ static bool
+ default_empty (const value&);
+
+ // Default implementations of the assign/append/prepend callbacks for simple
+ // types. They call value_traits<T>::convert() and then pass the result to
+ // value_traits<T>::assign()/append()/prepend(). As a result, it may not be
+ // the most efficient way to do it.
+ //
+ template <typename T>
+ static void
+ simple_assign (value&, names&&, const variable*);
+
+ template <typename T>
+ static void
+ simple_append (value&, names&&, const variable*);
+
+ template <typename T>
+ static void
+ simple_prepend (value&, names&&, const variable*);
+
+ // Default implementations of the reverse callback for simple types that
+ // calls value_traits<T>::reverse() and adds the result to the vector. As a
+ // result, it may not be the most efficient way to do it.
+ //
+ template <typename T>
+ static names_view
+ simple_reverse (const value&, names&);
+
+ // Default implementations of the compare callback for simple types that
+ // calls value_traits<T>::compare().
+ //
+ template <typename T>
+ static int
+ simple_compare (const value&, const value&);
+
+ // names
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<names>
+ {
+ static const names& empty_instance;
+ };
+
+ // bool
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<bool>
+ {
+ static_assert (sizeof (bool) <= value::size_, "insufficient space");
+
+ static bool convert (name&&, name*);
+ static void assign (value&, bool);
+ static void append (value&, bool); // OR.
+ static name reverse (bool x) {return name (x ? "true" : "false");}
+ static int compare (bool, bool);
+ static bool empty (bool) {return false;}
+
+ static const bool empty_value = false;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<uint64_t>
+ {
+ static_assert (sizeof (uint64_t) <= value::size_, "insufficient space");
+
+ static uint64_t convert (name&&, name*);
+ static void assign (value&, uint64_t);
+ static void append (value&, uint64_t); // ADD.
+ static name reverse (uint64_t x) {return name (to_string (x));}
+ static int compare (uint64_t, uint64_t);
+ static bool empty (bool) {return false;}
+
+ static const bool empty_value = false;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // Treat unsigned integral types as uint64. Note that bool is handled
+ // differently at an earlier stage.
+ //
+ template <typename T>
+ struct value_traits_specialization<T,
+ typename std::enable_if<
+ std::is_integral<T>::value &&
+ std::is_unsigned<T>::value>::type>:
+ value_traits<uint64_t> {};
+
+ // string
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<string>
+ {
+ static_assert (sizeof (string) <= value::size_, "insufficient space");
+
+ static string convert (name&&, name*);
+ static void assign (value&, string&&);
+ static void append (value&, string&&);
+ static void prepend (value&, string&&);
+ static name reverse (const string& x) {return name (x);}
+ static int compare (const string&, const string&);
+ static bool empty (const string& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const string& empty_instance;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // Treat const char* as string.
+ //
+ template <>
+ struct value_traits<const char*>: value_traits<string> {};
+
+ // path
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<path>
+ {
+ static_assert (sizeof (path) <= value::size_, "insufficient space");
+
+ static path convert (name&&, name*);
+ static void assign (value&, path&&);
+ static void append (value&, path&&); // operator/
+ static void prepend (value&, path&&); // operator/
+ static name reverse (const path& x) {
+ return x.to_directory ()
+ ? name (path_cast<dir_path> (x))
+ : name (x.string ());
+ }
+ static int compare (const path&, const path&);
+ static bool empty (const path& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const path& empty_instance;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // dir_path
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<dir_path>
+ {
+ static_assert (sizeof (dir_path) <= value::size_, "insufficient space");
+
+ static dir_path convert (name&&, name*);
+ static void assign (value&, dir_path&&);
+ static void append (value&, dir_path&&); // operator/
+ static void prepend (value&, dir_path&&); // operator/
+ static name reverse (const dir_path& x) {return name (x);}
+ static int compare (const dir_path&, const dir_path&);
+ static bool empty (const dir_path& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const dir_path& empty_instance;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // abs_dir_path
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<abs_dir_path>
+ {
+ static_assert (sizeof (abs_dir_path) <= value::size_,
+ "insufficient space");
+
+ static abs_dir_path convert (name&&, name*);
+ static void assign (value&, abs_dir_path&&);
+ static void append (value&, abs_dir_path&&); // operator/
+ static name reverse (const abs_dir_path& x) {return name (x);}
+ static int compare (const abs_dir_path&, const abs_dir_path&);
+ static bool empty (const abs_dir_path& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // name
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<name>
+ {
+ static_assert (sizeof (name) <= value::size_, "insufficient space");
+
+ static name convert (name&&, name*);
+ static void assign (value&, name&&);
+ static name reverse (const name& x) {return x;}
+ static int compare (const name& l, const name& r) {return l.compare (r);}
+ static bool empty (const name& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // name_pair
+ //
+ // An empty first or second half of a pair is treated as unspecified (this
+ // way it can be usage-specific whether a single value is first or second
+ // half of a pair). If both are empty then this is an empty value (and not a
+ // pair of two empties).
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<name_pair>
+ {
+ static_assert (sizeof (name_pair) <= value::size_, "insufficient space");
+
+ static name_pair convert (name&&, name*);
+ static void assign (value&, name_pair&&);
+ static int compare (const name_pair&, const name_pair&);
+ static bool empty (const name_pair& x) {
+ return x.first.empty () && x.second.empty ();}
+
+ static const bool empty_value = true;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // process_path
+ //
+ // Note that instances that we store always have non-empty recall and
+ // initial is its shallow copy.
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<process_path>
+ {
+ static_assert (sizeof (process_path) <= value::size_,
+ "insufficient space");
+
+ // This one is represented as a @-pair of names. As a result it cannot
+ // be stored in a container.
+ //
+ static process_path convert (name&&, name*);
+ static void assign (value&, process_path&&);
+ static int compare (const process_path&, const process_path&);
+ static bool empty (const process_path& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // target_triplet
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<target_triplet>
+ {
+ static_assert (sizeof (target_triplet) <= value::size_,
+ "insufficient space");
+
+ static target_triplet convert (name&&, name*);
+ static void assign (value&, target_triplet&&);
+ static name reverse (const target_triplet& x) {return name (x.string ());}
+ static int compare (const target_triplet& x, const target_triplet& y) {
+ return x.compare (y);}
+ static bool empty (const target_triplet& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // project_name
+ //
+ template <>
+ struct LIBBUILD2_SYMEXPORT value_traits<project_name>
+ {
+ static_assert (sizeof (project_name) <= value::size_,
+ "insufficient space");
+
+ static project_name convert (name&&, name*);
+ static void assign (value&, project_name&&);
+ static name reverse (const project_name&);
+ static int compare (const project_name& x, const project_name& y) {
+ return x.compare (y);}
+ static bool empty (const project_name& x) {return x.empty ();}
+
+ static const bool empty_value = true;
+ static const project_name& empty_instance;
+ static const char* const type_name;
+ static const build2::value_type value_type;
+ };
+
+ // vector<T>
+ //
+ template <typename T>
+ struct value_traits<vector<T>>
+ {
+ static_assert (sizeof (vector<T>) <= value::size_, "insufficient space");
+
+ static vector<T> convert (names&&);
+ static void assign (value&, vector<T>&&);
+ static void append (value&, vector<T>&&);
+ static void prepend (value&, vector<T>&&);
+ static bool empty (const vector<T>& x) {return x.empty ();}
+
+ static const vector<T> empty_instance;
+
+ // Make sure these are static-initialized together. Failed that VC will
+ // make sure it's done in the wrong order.
+ //
+ struct value_type_ex: build2::value_type
+ {
+ string type_name;
+ value_type_ex (value_type&&);
+ };
+ static const value_type_ex value_type;
+ };
+
+ // map<K, V>
+ //
+ template <typename K, typename V>
+ struct value_traits<std::map<K, V>>
+ {
+ template <typename K1, typename V1> using map = std::map<K1, V1>;
+
+ static_assert (sizeof (map<K, V>) <= value::size_, "insufficient space");
+
+ static void assign (value&, map<K, V>&&);
+ static void append (value&, map<K, V>&&);
+ static void prepend (value& v, map<K, V>&& x) {
+ return append (v, move (x));}
+ static bool empty (const map<K, V>& x) {return x.empty ();}
+
+ static const map<K, V> empty_instance;
+
+ // Make sure these are static-initialized together. Failed that VC will
+ // make sure it's done in the wrong order.
+ //
+ struct value_type_ex: build2::value_type
+ {
+ string type_name;
+ value_type_ex (value_type&&);
+ };
+ static const value_type_ex value_type;
+ };
+
+ // Explicitly pre-instantiate and export value_traits templates for
+ // vector/map value types used in the build2 project. Note that this is not
+ // merely an optimization since not doing so we may end up with multiple
+ // value type objects for the same traits type (and we use their addressed
+ // as identity; see cast(const value&) for an example).
+ //
+ extern template struct LIBBUILD2_DECEXPORT value_traits<strings>;
+ extern template struct LIBBUILD2_DECEXPORT value_traits<vector<name>>;
+ extern template struct LIBBUILD2_DECEXPORT value_traits<paths>;
+ extern template struct LIBBUILD2_DECEXPORT value_traits<dir_paths>;
+ extern template struct LIBBUILD2_DECEXPORT value_traits<uint64s>;
+
+ extern template struct LIBBUILD2_DECEXPORT
+ value_traits<std::map<string, string>>;
+
+ extern template struct LIBBUILD2_DECEXPORT
+ value_traits<std::map<project_name, dir_path>>;
+
+ // Project-wide (as opposed to global) variable overrides. Returned by
+ // context.cxx:reset().
+ //
+ struct variable_override
+ {
+ const variable& var; // Original variable.
+ const variable& ovr; // Override variable.
+ optional<dir_path> dir; // Scope directory relative to base.
+ value val;
+ };
+
+ using variable_overrides = vector<variable_override>;
+
+ // Variable pool.
+ //
+ // The global version is protected by the phase mutex.
+ //
+ class variable_pool
+ {
+ public:
+ // Find existing (assert exists).
+ //
+ const variable&
+ operator[] (const string& name) const;
+
+ // Return NULL if there is no variable with this name.
+ //
+ const variable*
+ find (const string& name) const;
+
+ // Find existing or insert new (untyped, non-overridable, normal
+ // visibility; but may be overridden by a pattern).
+ //
+ const variable&
+ insert (string name)
+ {
+ return insert (move (name), nullptr, nullptr, nullptr);
+ }
+
+ // Insert or override (type/visibility). Note that by default the
+ // variable is not overridable.
+ //
+ const variable&
+ insert (string name, variable_visibility v)
+ {
+ return insert (move (name), nullptr, &v, nullptr);
+ }
+
+ const variable&
+ insert (string name, bool overridable)
+ {
+ return insert (move (name), nullptr, nullptr, &overridable);
+ }
+
+ const variable&
+ insert (string name, bool overridable, variable_visibility v)
+ {
+ return insert (move (name), nullptr, &v, &overridable);
+ }
+
+ template <typename T>
+ const variable&
+ insert (string name)
+ {
+ return insert (move (name), &value_traits<T>::value_type);
+ }
+
+ template <typename T>
+ const variable&
+ insert (string name, variable_visibility v)
+ {
+ return insert (move (name), &value_traits<T>::value_type, &v);
+ }
+
+ template <typename T>
+ const variable&
+ insert (string name, bool overridable)
+ {
+ return insert (
+ move (name), &value_traits<T>::value_type, nullptr, &overridable);
+ }
+
+ template <typename T>
+ const variable&
+ insert (string name, bool overridable, variable_visibility v)
+ {
+ return insert (
+ move (name), &value_traits<T>::value_type, &v, &overridable);
+ }
+
+ // Alias an existing variable with a new name.
+ //
+ // Aliasing is purely a lookup-level mechanism. That is, when variable_map
+ // looks for a value, it tries all the aliases (and returns the storage
+ // variable in lookup).
+ //
+ // The existing variable should already have final type and visibility
+ // values which are copied over to the alias.
+ //
+ // Overridable aliased variables are most likely a bad idea: without a
+ // significant effort, the overrides will only be applied along the alias
+ // names (i.e., there would be no cross-alias overriding). So for now we
+ // don't allow this (use the common variable mechanism instead).
+ //
+ LIBBUILD2_SYMEXPORT const variable&
+ insert_alias (const variable& var, string name);
+
+ // Insert a variable pattern. Any variable that matches this pattern
+ // will have the specified type, visibility, and overridability. If
+ // match is true, then individual insertions of the matching variable
+ // must match the specified type/visibility/overridability. Otherwise,
+ // individual insertions can provide alternative values and the pattern
+ // values are a fallback (if you specify false you better be very clear
+ // about what you are trying to achieve).
+ //
+ // The pattern must be in the form [<prefix>.](*|**)[.<suffix>] where
+ // '*' matches single component stems (i.e., 'foo' but not 'foo.bar')
+ // and '**' matches single and multi-component stems. Note that only
+ // multi-component variables are considered for pattern matching (so
+ // just '*' won't match anything).
+ //
+ // The patterns are matched in the more-specific-first order where the
+ // pattern is considered more specific if it has a greater sum of its
+ // prefix and suffix lengths. If the prefix and suffix are equal, then the
+ // '*' pattern is considered more specific than '**'. If neither is more
+ // specific, then they are matched in the reverse order of insertion.
+ //
+ // If retro is true then a newly inserted pattern is also applied
+ // retrospectively to all the existing variables that match but only
+ // if no more specific pattern already exists (which is then assumed
+ // to have been applied). So if you use this functionality, watch out
+ // for the insertion order (you probably want more specific first).
+ //
+ public:
+ LIBBUILD2_SYMEXPORT void
+ insert_pattern (const string& pattern,
+ optional<const value_type*> type,
+ optional<bool> overridable,
+ optional<variable_visibility>,
+ bool retro = false,
+ bool match = true);
+
+ template <typename T>
+ void
+ insert_pattern (const string& p,
+ optional<bool> overridable,
+ optional<variable_visibility> v,
+ bool retro = false,
+ bool match = true)
+ {
+ insert_pattern (
+ p, &value_traits<T>::value_type, overridable, v, retro, match);
+ }
+
+ public:
+ void
+ clear () {map_.clear ();}
+
+ variable_pool (): variable_pool (false) {}
+
+ // RW access.
+ //
+ variable_pool&
+ rw () const
+ {
+ assert (phase == run_phase::load);
+ return const_cast<variable_pool&> (*this);
+ }
+
+ variable_pool&
+ rw (scope&) const {return const_cast<variable_pool&> (*this);}
+
+ private:
+ LIBBUILD2_SYMEXPORT static variable_pool instance;
+
+ LIBBUILD2_SYMEXPORT variable&
+ insert (string name,
+ const value_type*,
+ const variable_visibility* = nullptr,
+ const bool* overridable = nullptr,
+ bool pattern = true);
+
+ LIBBUILD2_SYMEXPORT void
+ update (variable&,
+ const value_type*,
+ const variable_visibility* = nullptr,
+ const bool* = nullptr) const;
+
+ // Entities that can access bypassing the lock proof.
+ //
+ friend class parser;
+ friend class scope;
+ friend LIBBUILD2_SYMEXPORT variable_overrides reset (const strings&);
+
+ public:
+ // For var_pool initialization.
+ //
+ LIBBUILD2_SYMEXPORT static const variable_pool& cinstance;
+
+ // Variable map.
+ //
+ private:
+ using key = butl::map_key<string>;
+ using map = std::unordered_map<key, variable>;
+
+ pair<map::iterator, bool>
+ insert (variable&& var)
+ {
+ // Keeping a pointer to the key while moving things during insertion is
+ // tricky. We could use a C-string instead of C++ for a key but that
+ // gets hairy very quickly (there is no std::hash for C-strings). So
+ // let's rely on small object-optimized std::string for now.
+ //
+ string n (var.name);
+ auto r (map_.insert (map::value_type (&n, move (var))));
+
+ if (r.second)
+ r.first->first.p = &r.first->second.name;
+
+ return r;
+ }
+
+ map map_;
+
+ // Patterns.
+ //
+ public:
+ struct pattern
+ {
+ string prefix;
+ string suffix;
+ bool multi; // Match multi-component stems.
+ bool match; // Must match individual variable insersions.
+
+ optional<const value_type*> type;
+ optional<variable_visibility> visibility;
+ optional<bool> overridable;
+
+ friend bool
+ operator< (const pattern& x, const pattern& y)
+ {
+ if (x.prefix.size () + x.suffix.size () <
+ y.prefix.size () + y.suffix.size ())
+ return true;
+
+ if (x.prefix == y.prefix && x.suffix == y.suffix)
+ return x.multi && !y.multi;
+
+ return false;
+ }
+ };
+
+ private:
+ std::multiset<pattern> patterns_;
+
+ // Global pool flag.
+ //
+ private:
+ explicit
+ variable_pool (bool global): global_ (global) {}
+
+ bool global_;
+ };
+
+ LIBBUILD2_SYMEXPORT extern const variable_pool& var_pool;
+}
+
+// variable_map
+//
+namespace butl
+{
+ template <>
+ struct compare_prefix<std::reference_wrapper<const build2::variable>>:
+ compare_prefix<std::string>
+ {
+ typedef compare_prefix<std::string> base;
+
+ explicit
+ compare_prefix (char d): base (d) {}
+
+ bool
+ operator() (const build2::variable& x, const build2::variable& y) const
+ {
+ return base::operator() (x.name, y.name);
+ }
+
+ bool
+ prefix (const build2::variable& p, const build2::variable& k) const
+ {
+ return base::prefix (p.name, k.name);
+ }
+ };
+}
+
+namespace build2
+{
+ class LIBBUILD2_SYMEXPORT variable_map
+ {
+ public:
+ struct value_data: value
+ {
+ using value::value;
+ using value::operator=;
+
+ size_t version = 0; // Incremented on each modification (variable_cache).
+ };
+
+ // Note that we guarantee ascending iteration order (e.g., for predictable
+ // dump output in tests).
+ //
+ using map_type = butl::prefix_map<reference_wrapper<const variable>,
+ value_data,
+ '.'>;
+ using size_type = map_type::size_type;
+
+ template <typename I>
+ class iterator_adapter: public I
+ {
+ public:
+ iterator_adapter () = default;
+ iterator_adapter (const I& i, const variable_map& m): I (i), m_ (&m) {}
+
+ // Automatically type a newly typed value on access.
+ //
+ typename I::reference operator* () const;
+ typename I::pointer operator-> () const;
+
+ // Untyped access.
+ //
+ uint16_t extra () const {return I::operator* ().second.extra;}
+ typename I::reference untyped () const {return I::operator* ();}
+
+ private:
+ const variable_map* m_;
+ };
+
+ using const_iterator = iterator_adapter<map_type::const_iterator>;
+
+ // Lookup. Note that variable overrides will not be applied, even if
+ // set in this map.
+ //
+ lookup
+ operator[] (const variable& var) const
+ {
+ auto p (find (var));
+ return lookup (p.first, &p.second, this);
+ }
+
+ lookup
+ operator[] (const variable* var) const // For cached variables.
+ {
+ assert (var != nullptr);
+ return operator[] (*var);
+ }
+
+ lookup
+ operator[] (const string& name) const
+ {
+ const variable* var (var_pool.find (name));
+ return var != nullptr ? operator[] (*var) : lookup ();
+ }
+
+ // If typed is false, leave the value untyped even if the variable is.
+ // The second half of the pair is the storage variable.
+ //
+ pair<const value_data*, const variable&>
+ find (const variable&, bool typed = true) const;
+
+ pair<value_data*, const variable&>
+ find_to_modify (const variable&, bool typed = true);
+
+ // Convert a lookup pointing to a value belonging to this variable map
+ // to its non-const version. Note that this is only safe on the original
+ // values (see find_original()).
+ //
+ value&
+ modify (const lookup& l)
+ {
+ assert (l.vars == this);
+ value& r (const_cast<value&> (*l.value));
+ static_cast<value_data&> (r).version++;
+ return r;
+ }
+
+ // Return a value suitable for assignment. See scope for details.
+ //
+ value&
+ assign (const variable& var) {return insert (var).first;}
+
+ value&
+ assign (const variable* var) // For cached variables.
+ {
+ assert (var != nullptr);
+ return assign (*var);
+ }
+
+ // Note that the variable is expected to have already been registered.
+ //
+ value&
+ assign (const string& name) {return insert (var_pool[name]).first;}
+
+ // As above but also return an indication of whether the new value (which
+ // will be NULL) was actually inserted. Similar to find(), if typed is
+ // false, leave the value untyped even if the variable is.
+ //
+ pair<reference_wrapper<value>, bool>
+ insert (const variable&, bool typed = true);
+
+ pair<const_iterator, const_iterator>
+ find_namespace (const variable& ns) const
+ {
+ auto r (m_.find_sub (ns));
+ return make_pair (const_iterator (r.first, *this),
+ const_iterator (r.second, *this));
+ }
+
+ const_iterator
+ begin () const {return const_iterator (m_.begin (), *this);}
+
+ const_iterator
+ end () const {return const_iterator (m_.end (), *this);}
+
+ bool
+ empty () const {return m_.empty ();}
+
+ size_type
+ size () const {return m_.size ();}
+
+ public:
+ // Global should be true if this map is part of the global build state
+ // (e.g., scopes, etc).
+ //
+ explicit
+ variable_map (bool global = false): global_ (global) {}
+
+ void
+ clear () {m_.clear ();}
+
+ private:
+ friend class variable_type_map;
+
+ void
+ typify (const value_data&, const variable&) const;
+
+ private:
+ bool global_;
+ map_type m_;
+ };
+
+ // Value caching. Used for overrides as well as target type/pattern-specific
+ // append/prepend.
+ //
+ // In many places we assume that we can store a reference to the returned
+ // variable value (e.g., install::lookup_install()). As a result, in these
+ // cases where we calculate the value dynamically, we have to cache it
+ // (note, however, that if the value becomes stale, there is no guarantee
+ // the references remain valid).
+ //
+ // Note that since the cache can be modified on any lookup (including during
+ // the execute phase), it is protected by its own mutex shard (allocated in
+ // main()). This shard is also used for value typification (which is kind of
+ // like caching) during concurrent execution phases.
+ //
+ LIBBUILD2_SYMEXPORT extern size_t variable_cache_mutex_shard_size;
+
+ LIBBUILD2_SYMEXPORT extern unique_ptr<shared_mutex[]>
+ variable_cache_mutex_shard;
+
+ template <typename K>
+ class variable_cache
+ {
+ public:
+ // If the returned unique lock is locked, then the value has been
+ // invalidated. If the variable type does not match the value type,
+ // then typify the cached value.
+ //
+ pair<value&, ulock>
+ insert (K, const lookup& stem, size_t version, const variable&);
+
+ private:
+ struct entry_type
+ {
+ // Note: we use value_data instead of value since the result is often
+ // returned as lookup. We also maintain the version in case one cached
+ // value (e.g., override) is based on another (e.g., target
+ // type/pattern-specific prepend/append).
+ //
+ variable_map::value_data value;
+
+ size_t version = 0; // Version on which this value is based.
+
+ // Location of the stem as well as the version on which this cache
+ // value is based. Used to track the location and value of the stem
+ // for cache invalidation. NULL/0 means there is no stem.
+ //
+ const variable_map* stem_vars = nullptr;
+ size_t stem_version = 0;
+
+ // For GCC 4.9.
+ //
+ entry_type () = default;
+ entry_type (variable_map::value_data val,
+ size_t ver,
+ const variable_map* svars,
+ size_t sver)
+ : value (move (val)),
+ version (ver),
+ stem_vars (svars),
+ stem_version (sver) {}
+ };
+
+ using map_type = std::map<K, entry_type>;
+
+ map_type m_;
+ };
+
+ // Target type/pattern-specific variables.
+ //
+ class variable_pattern_map
+ {
+ public:
+ using map_type = std::map<string, variable_map>;
+ using const_iterator = map_type::const_iterator;
+ using const_reverse_iterator = map_type::const_reverse_iterator;
+
+ explicit
+ variable_pattern_map (bool global): global_ (global) {}
+
+ variable_map&
+ operator[] (const string& v)
+ {
+ return map_.emplace (v, variable_map (global_)).first->second;
+ }
+
+ const_iterator begin () const {return map_.begin ();}
+ const_iterator end () const {return map_.end ();}
+ const_reverse_iterator rbegin () const {return map_.rbegin ();}
+ const_reverse_iterator rend () const {return map_.rend ();}
+ bool empty () const {return map_.empty ();}
+
+ private:
+ bool global_;
+ map_type map_;
+ };
+
+ class LIBBUILD2_SYMEXPORT variable_type_map
+ {
+ public:
+ using map_type = std::map<reference_wrapper<const target_type>,
+ variable_pattern_map>;
+ using const_iterator = map_type::const_iterator;
+
+ explicit
+ variable_type_map (bool global): global_ (global) {}
+
+ variable_pattern_map&
+ operator[] (const target_type& t)
+ {
+ return map_.emplace (t, variable_pattern_map (global_)).first->second;
+ }
+
+ const_iterator begin () const {return map_.begin ();}
+ const_iterator end () const {return map_.end ();}
+ bool empty () const {return map_.empty ();}
+
+ lookup
+ find (const target_type&, const string& tname, const variable&) const;
+
+ // Prepend/append value cache.
+ //
+ // The key is the combination of the "original value identity" (as a
+ // pointer to the value in one of the variable_pattern_map's) and the
+ // "target identity" (as target type and target name). Note that while at
+ // first it may seem like we don't need the target identity, we actually
+ // do since the stem may itself be target-type/pattern-specific. See
+ // scope::find_original() for details.
+ //
+ mutable
+ variable_cache<tuple<const value*, const target_type*, string>>
+ cache;
+
+ private:
+ bool global_;
+ map_type map_;
+ };
+}
+
+#include <libbuild2/variable.ixx>
+#include <libbuild2/variable.txx>
+
+#endif // LIBBUILD2_VARIABLE_HXX