Add portable environment variable manipulation functions

6 files changed, 124 insertions, 52 deletions

diff --git a/libbutl/path.cxx b/libbutl/path.cxx
index 11a34c9..47d691b 100644
--- a/libbutl/path.cxx
+++ b/libbutl/path.cxx
@@ -17,7 +17,7 @@
 #else
 #  include <pwd.h>       // struct passwd, getpwuid_r()
 #  include <errno.h>     // EINVAL
-#  include <stdlib.h>    // realpath(), getenv()
+#  include <stdlib.h>    // realpath()
 #  include <limits.h>    // PATH_MAX
 #  include <unistd.h>    // getcwd(), chdir()
 #  include <string.h>    // strlen(), strcpy()
@@ -29,6 +29,7 @@
 
 #ifndef __cpp_lib_modules
 #include <string>
+#include <vector>
 #include <cstddef>
 #include <utility>
 
@@ -123,33 +124,39 @@ namespace butl
   }
 
 #ifndef _WIN32
-  static const char*
+  static const vector<string> tmp_vars ({"TMPDIR", "TMP", "TEMP", "TEMPDIR"});
+
+  static string
   temp_directory ()
   {
-    const char* dir (nullptr);
-    const char* env[] = {"TMPDIR", "TMP", "TEMP", "TEMPDIR", nullptr};
+    optional<string> dir;
 
-    for (auto e (env); dir == nullptr && *e != nullptr; ++e)
-      dir = getenv (*e);
+    for (const string& v: tmp_vars)
+    {
+      dir = getenv (v);
+
+      if (dir)
+        break;
+    }
 
-    if (dir == nullptr)
+    if (!dir)
       dir = "/tmp";
 
     struct stat s;
-    if (stat (dir, &s) != 0)
+    if (stat (dir->c_str (), &s) != 0)
       throw_generic_error (errno);
 
     if (!S_ISDIR (s.st_mode))
       throw_generic_error (ENOTDIR);
 
-    return dir;
+    return *dir;
   }
 
   static string
   home ()
   {
-    if (const char* h = getenv ("HOME"))
-      return h;
+    if (optional<string> h = getenv ("HOME"))
+      return *h;
 
     // Struct passwd has 5 members that will use this buffer. Two are the
     // home directory and shell paths. The other three are the user login
@@ -214,8 +221,8 @@ namespace butl
 #else
     // Could be set by, e.g., MSYS and Cygwin shells.
     //
-    if (const char* h = getenv ("HOME"))
-      return h;
+    if (optional<string> h = getenv ("HOME"))
+      return *h;
 
     char h[_MAX_PATH];
     HRESULT r (SHGetFolderPathA (NULL, CSIDL_PROFILE, NULL, 0, h));
diff --git a/libbutl/process.cxx b/libbutl/process.cxx
index 41e2c0d..384af29 100644
--- a/libbutl/process.cxx
+++ b/libbutl/process.cxx
@@ -9,7 +9,6 @@
 #include <errno.h>
 
 #ifndef _WIN32
-#  include <stdlib.h>    // setenv(), unsetenv()
 #  include <signal.h>    // SIG*
 #  include <unistd.h>    // execvp, fork, dup2, pipe, chdir, *_FILENO, getpid
 #  include <sys/wait.h>  // waitpid
@@ -60,7 +59,7 @@
 #include <map>
 #include <ratio>     // milli
 #include <chrono>
-#include <cstdlib>   // getenv(), __argv[]
+#include <cstdlib>   // __argv[]
 #include <algorithm> // find()
 #endif
 #endif
@@ -83,7 +82,6 @@ import std.io;
 import std.threading; // Clang wants it in purview (see process-details.hxx).
 #endif
 import butl.path;
-import butl.optional;
 import butl.fdstream;
 import butl.vector_view;
 import butl.small_vector;
@@ -273,7 +271,8 @@ namespace butl
     // 2. We do not continue searching on EACCES from execve().
     // 3. We do not execute via default shell on ENOEXEC from execve().
     //
-    for (const char* b (getenv ("PATH")), *e;
+    optional<string> p (getenv ("PATH"));
+    for (const char* b (p ? p->c_str () : nullptr), *e;
          b != nullptr;
          b = (e != nullptr ? e + 1 : e))
     {
@@ -460,12 +459,17 @@ namespace butl
           {
             const char* v (strchr (ev, '='));
 
-            int r (v != nullptr
-                   ? setenv (string (ev, v - ev).c_str (), v + 1, 1)
-                   : unsetenv (ev));
-
-            if (r == -1)
-              fail (true);
+            try
+            {
+              if (v != nullptr)
+                setenv (string (ev, v - ev), v + 1);
+              else
+                unsetenv (ev);
+            }
+            catch (const system_error& e)
+            {
+              throw process_child_error (e.code ().value ());
+            }
           }
         }
 
@@ -845,7 +849,8 @@ namespace butl
 
     // Now search in PATH. Recall is unchanged.
     //
-    for (const char* b (getenv ("PATH")), *e;
+    optional<string> p (getenv ("PATH"));
+    for (const char* b (p ? p->c_str () : nullptr), *e;
          b != nullptr;
          b = (e != nullptr ? e + 1 : e))
     {
@@ -1126,7 +1131,7 @@ namespace butl
     // cmd.exe and passing the batch file as an argument (see CreateProcess()
     // for deails).
     //
-    const char* batch (nullptr);
+    optional<string> batch;
     {
       const char* p (pp.effect_string ());
       const char* e (path::traits::find_extension (p, strlen (p)));
@@ -1135,7 +1140,7 @@ namespace butl
       {
         batch = getenv ("COMSPEC");
 
-        if (batch == nullptr)
+        if (!batch)
           batch = "C:\\Windows\\System32\\cmd.exe";
       }
     }
@@ -1240,14 +1245,14 @@ namespace butl
           cmd_line += '"';
       };
 
-      if (batch != nullptr)
+      if (batch)
       {
-        append (batch);
+        append (*batch);
         append ("/c");
         append (pp.effect_string ());
       }
 
-      for (const char* const* p (args + (batch != nullptr ? 1 : 0));
+      for (const char* const* p (args + (batch ? 1 : 0));
            *p != 0;
            ++p)
         append (*p);
@@ -1463,7 +1468,7 @@ namespace butl
       };
 
       bool msys (false);
-      if (batch == nullptr)
+      if (!batch)
       {
         string p (pp.effect_string ());
         auto i (detect_msys_cache_.find (p));
@@ -1482,7 +1487,7 @@ namespace butl
       for (system_clock::duration timeout (1h);;) // Try for about 1 hour.
       {
         if (!CreateProcess (
-              batch != nullptr ? batch : pp.effect_string (),
+              batch ? batch->c_str () : pp.effect_string (),
               const_cast<char*> (cmd_line.c_str ()),
               0,    // Process security attributes.
               0,    // Primary thread security attributes.
diff --git a/libbutl/utility.cxx b/libbutl/utility.cxx
index 8e2422aa..502586c 100644
--- a/libbutl/utility.cxx
+++ b/libbutl/utility.cxx
@@ -10,6 +10,8 @@
 #include <libbutl/win32-utility.hxx>
 #endif
 
+#include <stdlib.h> // setenv(), unsetenv(), _putenv()
+
 #ifndef __cpp_lib_modules
 #include <string>
 #include <cstddef>
@@ -124,6 +126,36 @@ namespace butl
 
     return l;
   }
+
+  void
+  setenv (const string& name, const string& value)
+  {
+#ifndef _WIN32
+    if (::setenv (name.c_str (), value.c_str (), 1 /* overwrite */) == -1)
+      throw_generic_error (errno);
+#else
+    // The documentation doesn't say how to obtain the failure reason, so we
+    // will assume it to always be EINVAL (as the most probable one).
+    //
+    if (_putenv (string (name + '=' + value).c_str ()) == -1)
+      throw_generic_error (EINVAL);
+#endif
+  }
+
+  void
+  unsetenv (const string& name)
+  {
+#ifndef _WIN32
+    if (::unsetenv (name.c_str ()) == -1)
+      throw_generic_error (errno);
+#else
+    // The documentation doesn't say how to obtain the failure reason, so we
+    // will assume it to always be EINVAL (as the most probable one).
+    //
+    if (_putenv (string (name + '=').c_str ()) == -1)
+      throw_generic_error (EINVAL);
+#endif
+  }
 }
 
 namespace std
diff --git a/libbutl/utility.ixx b/libbutl/utility.ixx
index d4aaa65..565a694 100644
--- a/libbutl/utility.ixx
+++ b/libbutl/utility.ixx
@@ -2,6 +2,10 @@
 // copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
+#ifndef __cpp_lib_modules
+#include <cstdlib> // getenv()
+#endif
+
 namespace butl
 {
   inline char
@@ -199,4 +203,13 @@ namespace butl
 
     throw std::istream::failure ("");
   }
+
+  inline optional<std::string>
+  getenv (const std::string& name)
+  {
+    if (const char* r = std::getenv (name.c_str ()))
+      return std::string (r);
+
+    return nullopt;
+  }
 }
diff --git a/libbutl/utility.mxx b/libbutl/utility.mxx
index 740b411..252a4b4 100644
--- a/libbutl/utility.mxx
+++ b/libbutl/utility.mxx
@@ -35,6 +35,9 @@ export module butl.utility;
 import std.core;
 import std.io;
 #endif
+import butl.optional;
+#else
+#include <libbutl/optional.mxx>
 #endif
 
 #include <libbutl/export.hxx>
@@ -183,6 +186,25 @@ LIBBUTL_MODEXPORT namespace butl
   bool
   eof (std::istream&);
 
+  // Environment variables.
+  //
+  optional<std::string>
+  getenv (const std::string&);
+
+  // Throw system_error on failure.
+  //
+  // Note that on Windows setting an empty value usets the variable.
+  //
+  LIBBUTL_SYMEXPORT
+  void
+  setenv (const std::string& name, const std::string& value);
+
+  // Throw system_error on failure.
+  //
+  LIBBUTL_SYMEXPORT
+  void
+  unsetenv (const std::string&);
+
   // Key comparators (i.e., to be used in sets, maps, etc).
   //
   struct compare_c_string
diff --git a/tests/process/driver.cxx b/tests/process/driver.cxx
index 9bee6c5..6ca28a5 100644
--- a/tests/process/driver.cxx
+++ b/tests/process/driver.cxx
@@ -2,8 +2,6 @@
 // copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
 // license   : MIT; see accompanying LICENSE file
 
-#include <stdlib.h> // getenv(), setenv(), _putenv()
-
 #include <cassert>
 
 #ifndef __cpp_lib_modules
@@ -23,11 +21,13 @@ import std.core;
 import std.io;
 #endif
 import butl.path;
+import butl.utility;  // setenv(), getenv()
 import butl.process;
 import butl.optional;
 import butl.fdstream;
 #else
 #include <libbutl/path.mxx>
+#include <libbutl/utility.mxx>
 #include <libbutl/process.mxx>
 #include <libbutl/optional.mxx>
 #include <libbutl/fdstream.mxx>
@@ -68,13 +68,8 @@ exec (const path& p,
     // sure that the child process will not see the variable that is requested
     // to be unset, and will see the other one unaffected.
     //
-#ifndef _WIN32
-    assert (setenv ("DEF", "2", 1) == 0);
-    assert (setenv ("XYZ", "3", 1) == 0);
-#else
-    assert (_putenv ("DEF=2") == 0);
-    assert (_putenv ("XYZ=3") == 0);
-#endif
+    setenv ("DEF", "2");
+    setenv ("XYZ", "3");
   }
 
   if (cwd != nullptr)
@@ -205,6 +200,9 @@ exec (const path& p,
 int
 main (int argc, const char* argv[])
 {
+  using butl::getenv;
+  using butl::optional;
+
   bool child (false);
   bool bin (false);
   dir_path wd;      // Working directory.
@@ -276,10 +274,9 @@ main (int argc, const char* argv[])
       // Check that the ABC variable is set, the DEF is unset and the XYZ is
       // left unchanged.
       //
-      const char* v;
-      if ((v = getenv ("ABC")) == nullptr || string ("1") != v ||
-          getenv ("DEF") != nullptr ||
-          (v = getenv ("XYZ")) == nullptr || string ("3") != v)
+      if (getenv ("ABC") != optional<string> ("1") ||
+          getenv ("DEF") ||
+          getenv ("XYZ") != optional<string> ("3"))
         return 1;
     }
 
@@ -383,14 +380,10 @@ main (int argc, const char* argv[])
   //
   string paths (fp.directory ().string ());
 
-  if (char const* s = getenv ("PATH"))
-    paths += string (1, path::traits::path_separator) + s;
+  if (optional<string> p = getenv ("PATH"))
+    paths += string (1, path::traits::path_separator) + *p;
 
-#ifndef _WIN32
-  assert (setenv ("PATH", paths.c_str (), 1) == 0);
-#else
-  assert (_putenv (("PATH=" + paths).c_str ()) == 0);
-#endif
+  setenv ("PATH", paths);
 
   dir_path::current_directory (fp.directory () / dir_path (".."));
 
@@ -419,7 +412,7 @@ main (int argc, const char* argv[])
     assert (exec (owd / "test"));
 
     paths = owd.string () + path::traits::path_separator + paths;
-    assert (_putenv (("PATH=" + paths).c_str ()) == 0);
+    setenv ("PATH", paths);
 
     assert (exec (path ("test.bat")));
     assert (exec (path ("test")));