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authorKaren Arutyunov <karen@codesynthesis.com>2017-05-01 18:24:31 +0300
committerKaren Arutyunov <karen@codesynthesis.com>2017-05-01 19:30:26 +0300
commit70317569c6dcd9809ed4a8c425777e653ec6ca08 (patch)
tree07a538b296933e9e2a1f81088f8fcc8da3f749ad /build2/context.hxx
parentcbec9ea8841c8a58b2d50bb628b28aea7a6fe179 (diff)
Add hxx extension for headers
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+// file : build2/context.hxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef BUILD2_CONTEXT_HXX
+#define BUILD2_CONTEXT_HXX
+
+#include <build2/types.hxx>
+#include <build2/utility.hxx>
+
+#include <build2/scope.hxx>
+#include <build2/variable.hxx>
+#include <build2/operation.hxx>
+#include <build2/scheduler.hxx>
+
+namespace build2
+{
+ // Main (and only) scheduler. Started up and shut down in main().
+ //
+ extern scheduler sched;
+
+ // In order to perform each operation the build system goes through the
+ // following phases:
+ //
+ // load - load the buildfiles
+ // match - search prerequisites and match rules
+ // execute - execute the matched rule
+ //
+ // The build system starts with a "serial load" phase and then continues
+ // with parallel search and execute. Match, however, can be interrupted
+ // both with load and execute.
+ //
+ // Match can be interrupted with "exclusive load" in order to load
+ // additional buildfiles. Similarly, it can be interrupted with (parallel)
+ // execute in order to build targetd required to complete the match (for
+ // example, generated source code or source code generators themselves.
+ //
+ // Such interruptions are performed by phase change that is protected by
+ // phase_mutex (which is also used to synchronize the state changes between
+ // phases).
+ //
+ // Serial load can perform arbitrary changes to the model. Exclusive load,
+ // however, can only perform "island appends". That is, it can create new
+ // "nodes" (variables, scopes, etc) but not change already existing nodes or
+ // invalidate any references to such (the idea here is that one should be
+ // able to load additional buildfiles as long as they don't interfere with
+ // the existing build state). The "islands" are identified by the
+ // load_generation number (0 for initial/serial load). It is incremented in
+ // case of a phase switch and is stored in various "nodes" (variables, etc)
+ // to allow modifications "within the islands".
+ //
+ extern run_phase phase;
+ extern size_t load_generation;
+
+ // A "tri-mutex" that keeps all the threads in one of the three phases. When
+ // a thread wants to switch a phase, it has to wait for all the other
+ // threads to do the same (or release their phase locks). The load phase is
+ // exclusive.
+ //
+ // The interleaving match and execute is interesting: during match we read
+ // the "external state" (e.g., filesystem entries, modifications times, etc)
+ // and capture it in the "internal state" (our dependency graph). During
+ // execute we are modifying the external state with controlled modifications
+ // of the internal state to reflect the changes (e.g., update mtimes). If
+ // you think about it, it's pretty clear that we cannot safely perform both
+ // of these actions simultaneously. A good example would be running a code
+ // generator and header dependency extraction simultaneously: the extraction
+ // process may pick up headers as they are being generated. As a result, we
+ // either have everyone treat the external state as read-only or write-only.
+ //
+ class phase_mutex
+ {
+ public:
+ // Acquire a phase lock potentially blocking (unless already in the
+ // desired phase) until switching to the desired phase is possible.
+ //
+ void
+ lock (run_phase);
+
+ // Release the phase lock potentially allowing (unless there are other
+ // locks on this phase) switching to a different phase.
+ //
+ void
+ unlock (run_phase);
+
+ // Switch from one phase to another. Semantically, just unlock() followed
+ // by lock() but more efficient.
+ //
+ void
+ relock (run_phase unlock, run_phase lock);
+
+ private:
+ friend struct phase_lock;
+ friend struct phase_unlock;
+ friend struct phase_switch;
+
+ phase_mutex (): lc_ (0), mc_ (0), ec_ (0) {phase = run_phase::load;}
+
+ static phase_mutex instance;
+
+ private:
+ // We have a counter for each phase which represents the number of threads
+ // in or waiting for this phase.
+ //
+ // We use condition variables to wait for a phase switch. The load phase
+ // is exclusive so we have a separate mutex to serialize it (think of it
+ // as a second level locking).
+ //
+ // When the mutex is unlocked (all three counters become zero, the phase
+ // is always changed to load (this is also the initial state).
+ //
+ mutex m_;
+ size_t lc_;
+ size_t mc_;
+ size_t ec_;
+
+ condition_variable lv_;
+ condition_variable mv_;
+ condition_variable ev_;
+
+ mutex lm_;
+ };
+
+ // Grab a new phase lock releasing it on destruction. The lock can be
+ // "owning" or "referencing" (recursive).
+ //
+ // On the referencing semantics: If there is already an instance of
+ // phase_lock in this thread, then the new instance simply references it.
+ //
+ // The reason for this semantics is to support the following scheduling
+ // pattern (in actual code we use wait_guard to RAII it):
+ //
+ // atomic_count task_count (0);
+ //
+ // {
+ // phase_lock l (run_phase::match); // (1)
+ //
+ // for (...)
+ // {
+ // sched.async (task_count,
+ // [] (...)
+ // {
+ // phase_lock pl (run_phase::match); // (2)
+ // ...
+ // },
+ // ...);
+ // }
+ // }
+ //
+ // sched.wait (task_count); // (3)
+ //
+ // Here is what's going on here:
+ //
+ // 1. We first get a phase lock "for ourselves" since after the first
+ // iteration of the loop, things may become asynchronous (including
+ // attempts to switch the phase and modify the structure we are iteration
+ // upon).
+ //
+ // 2. The task can be queued or it can be executed synchronously inside
+ // async() (refer to the scheduler class for details on this semantics).
+ //
+ // If this is an async()-synchronous execution, then the task will create
+ // a referencing phase_lock. If, however, this is a queued execution
+ // (including wait()-synchronous), then the task will create a top-level
+ // phase_lock.
+ //
+ // Note that we only acquire the lock once the task starts executing
+ // (there is no reason to hold the lock while the task is sitting in the
+ // queue). This optimization assumes that whatever else we pass to the
+ // task (for example, a reference to a target) is stable (in other words,
+ // such a reference cannot become invalid).
+ //
+ // 3. Before calling wait(), we release our phase lock to allow switching
+ // the phase.
+ //
+ struct phase_lock
+ {
+ explicit phase_lock (run_phase);
+ ~phase_lock ();
+
+ phase_lock (phase_lock&&) = delete;
+ phase_lock (const phase_lock&) = delete;
+
+ phase_lock& operator= (phase_lock&&) = delete;
+ phase_lock& operator= (const phase_lock&) = delete;
+
+ run_phase p;
+
+ static
+#ifdef __cpp_thread_local
+ thread_local
+#else
+ __thread
+#endif
+ phase_lock* instance;
+ };
+
+ // Assuming we have a lock on the current phase, temporarily release it
+ // and reacquire on destruction.
+ //
+ struct phase_unlock
+ {
+ phase_unlock (bool unlock = true);
+ ~phase_unlock ();
+
+ phase_lock* l;
+ };
+
+ // Assuming we have a lock on the current phase, temporarily switch to a
+ // new phase and switch back on destruction.
+ //
+ struct phase_switch
+ {
+ explicit phase_switch (run_phase);
+ ~phase_switch ();
+
+ run_phase o, n;
+ };
+
+ // Wait for a task count optionally and temporarily unlocking the phase.
+ //
+ struct wait_guard
+ {
+ ~wait_guard () noexcept (false);
+
+ explicit
+ wait_guard (atomic_count& task_count,
+ bool phase = false);
+
+ wait_guard (size_t start_count,
+ atomic_count& task_count,
+ bool phase = false);
+
+ void
+ wait ();
+
+ size_t start_count;
+ atomic_count* task_count;
+ bool phase;
+ };
+
+ // Cached variables.
+ //
+ extern const variable* var_src_root;
+ extern const variable* var_out_root;
+ extern const variable* var_src_base;
+ extern const variable* var_out_base;
+
+ extern const variable* var_project;
+ extern const variable* var_amalgamation;
+ extern const variable* var_subprojects;
+
+ extern const variable* var_import_target; // import.target
+
+ // Current action (meta/operation).
+ //
+ // The names unlike info are available during boot but may not yet be
+ // lifted. The name is always for an outer operation (or meta operation
+ // that hasn't been recognized as such yet).
+ //
+ extern const string* current_mname;
+ extern const string* current_oname;
+
+ extern const meta_operation_info* current_mif;
+ extern const operation_info* current_inner_oif;
+ extern const operation_info* current_outer_oif;
+ extern size_t current_on; // Current operation number (1-based) in the
+ // meta-operation batch.
+
+ extern execution_mode current_mode;
+
+ // Total number of dependency relationships in the current action. Together
+ // with the target::dependents count it is incremented during the rule
+ // search & match phase and is decremented during execution with the
+ // expectation of it reaching 0. Used as a sanity check.
+ //
+ extern atomic_count dependency_count;
+
+ inline void
+ set_current_mif (const meta_operation_info& mif)
+ {
+ current_mname = &mif.name;
+ current_mif = &mif;
+ current_on = 0; // Reset.
+ }
+
+ inline void
+ set_current_oif (const operation_info& inner_oif,
+ const operation_info* outer_oif = nullptr)
+ {
+ current_oname = &(outer_oif == nullptr ? inner_oif : *outer_oif).name;
+ current_inner_oif = &inner_oif;
+ current_outer_oif = outer_oif;
+ current_on++;
+ current_mode = inner_oif.mode;
+ dependency_count.store (0, memory_order_relaxed); // Serial.
+ }
+
+ // Keep going flag.
+ //
+ // Note that setting it to false is not of much help unless we are running
+ // serially. In parallel we queue most of the things up before we see any
+ // failures.
+ //
+ extern bool keep_going;
+
+ // Reset the build state. In particular, this removes all the targets,
+ // scopes, and variables.
+ //
+ variable_overrides
+ reset (const strings& cmd_vars);
+
+ // Return the project name or empty string if unnamed.
+ //
+ inline const string&
+ project (const scope& root)
+ {
+ auto l (root[var_project]);
+ return l ? cast<string> (l) : empty_string;
+ }
+
+ // Return the src/out directory corresponding to the given out/src. The
+ // passed directory should be a sub-directory of out/src_root.
+ //
+ dir_path
+ src_out (const dir_path& out, const scope& root);
+
+ dir_path
+ src_out (const dir_path& out,
+ const dir_path& out_root, const dir_path& src_root);
+
+ dir_path
+ out_src (const dir_path& src, const scope& root);
+
+ dir_path
+ out_src (const dir_path& src,
+ const dir_path& out_root, const dir_path& src_root);
+
+ // Action phrases, e.g., "configure update exe{foo}", "updating exe{foo}",
+ // and "updating exe{foo} is configured". Use like this:
+ //
+ // info << "while " << diag_doing (a, t);
+ //
+ class target;
+
+ struct diag_phrase
+ {
+ const action& a;
+ const target& t;
+ void (*f) (ostream&, const action&, const target&);
+ };
+
+ inline ostream&
+ operator<< (ostream& os, const diag_phrase& p)
+ {
+ p.f (os, p.a, p.t);
+ return os;
+ }
+
+ void
+ diag_do (ostream&, const action&, const target&);
+
+ inline diag_phrase
+ diag_do (const action& a, const target& t)
+ {
+ return diag_phrase {a, t, &diag_do};
+ }
+
+ void
+ diag_doing (ostream&, const action&, const target&);
+
+ inline diag_phrase
+ diag_doing (const action& a, const target& t)
+ {
+ return diag_phrase {a, t, &diag_doing};
+ }
+
+ void
+ diag_did (ostream&, const action&, const target&);
+
+ inline diag_phrase
+ diag_did (const action& a, const target& t)
+ {
+ return diag_phrase {a, t, &diag_did};
+ }
+
+ void
+ diag_done (ostream&, const action&, const target&);
+
+ inline diag_phrase
+ diag_done (const action& a, const target& t)
+ {
+ return diag_phrase {a, t, &diag_done};
+ }
+}
+
+#include <build2/context.ixx>
+
+#endif // BUILD2_CONTEXT_HXX