ninja: Set PATH for CustomTargets with built EXEs on Windows

When a CustomTarget is run with a command that is an executable built
by the project which also has a DLL built in the same project as a
dependency, the EXE can't run on Windows because the DLL can't be found.
On UNIX-like systems, we set the RPATH using the linker so these
dependencies can be found, but on Windows the only way is to set the
PATH environment variable.

The same problem exists for tests, so we reuse that infrastructure by
creating a new meson_exe.py script that can be used as a wrapper to run
CustomTarget commands on Windows. This can later also be extended to add
support for setting an environment while calling the command needed to
generate a CustomTarget: https://github.com/mesonbuild/meson/issues/266

2 files changed, 57 insertions, 1 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index ceb466b..08e3d2d 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -34,6 +34,18 @@ class InstallData():
         self.install_scripts = []
         self.install_subdirs = []
 
+class ExecutableSerialisation():
+    def __init__(self, name, fname, cmd_args, env, is_cross, exe_wrapper,
+                 workdir, extra_paths):
+        self.name = name
+        self.fname = fname
+        self.cmd_args = cmd_args
+        self.env = env
+        self.is_cross = is_cross
+        self.exe_runner = exe_wrapper
+        self.workdir = workdir
+        self.extra_paths = extra_paths
+
 class TestSerialisation:
     def __init__(self, name, suite, fname, is_cross, exe_wrapper, is_parallel, cmd_args, env,
                  should_fail, valgrind_args, timeout, workdir, extra_paths):
@@ -154,6 +166,35 @@ class Backend():
                 raise MesonException('Unknown data type in object list.')
         return obj_list
 
+    def serialise_executable(self, exe, cmd_args, workdir, env={}):
+        import uuid
+        # Can't just use exe.name here; it will likely be run more than once
+        scratch_file = 'meson_exe_{0}_{1}.dat'.format(exe.name,
+                                                      str(uuid.uuid4())[:8])
+        exe_data = os.path.join(self.environment.get_scratch_dir(), scratch_file)
+        with open(exe_data, 'wb') as f:
+            if isinstance(exe, dependencies.ExternalProgram):
+                exe_fullpath = exe.fullpath
+            else:
+                exe_fullpath = [os.path.join(self.environment.get_build_dir(),
+                                             self.get_target_filename(exe))]
+            is_cross = self.environment.is_cross_build() and \
+                self.environment.cross_info.need_cross_compiler() and \
+                self.environment.cross_info.need_exe_wrapper()
+            if is_cross:
+                exe_wrapper = self.environment.cross_info.config['binaries'].get('exe_wrapper', None)
+            else:
+                exe_wrapper = None
+            if mesonlib.is_windows():
+                extra_paths = self.determine_windows_extra_paths(exe)
+            else:
+                extra_paths = []
+            es = ExecutableSerialisation(exe.name, exe_fullpath, cmd_args, env,
+                                         is_cross, exe_wrapper, workdir,
+                                         extra_paths)
+            pickle.dump(es, f)
+        return exe_data
+
     def serialise_tests(self):
         test_data = os.path.join(self.environment.get_scratch_dir(), 'meson_test_setup.dat')
         datafile = open(test_data, 'wb')
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 201b2d1..9964322 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -341,6 +341,7 @@ int dummy;
     def generate_custom_target(self, target, outfile):
         (srcs, ofilenames, cmd) = self.eval_custom_target_command(target)
         deps = []
+        desc = 'Generating {0} with a {1} command.'
         for i in target.get_dependencies():
             # FIXME, should not grab element at zero but rather expand all.
             if isinstance(i, list):
@@ -364,9 +365,23 @@ int dummy;
                 tmp = [tmp]
             for fname in tmp:
                 elem.add_dep(os.path.join(self.get_target_dir(d), fname))
+        # Windows doesn't have -rpath, so for EXEs that need DLLs built within
+        # the project, we need to set PATH so the DLLs are found. We use
+        # a serialized executable wrapper for that and check if the
+        # CustomTarget command needs extra paths first.
+        if mesonlib.is_windows() and \
+           self.determine_windows_extra_paths(target.command[0]):
+            exe_data = self.serialise_executable(target.command[0], cmd[1:],
+                # All targets are built from the build dir
+                self.environment.get_build_dir())
+            cmd = [sys.executable, self.environment.get_build_command(),
+                   '--internal', 'exe', exe_data]
+            cmd_type = 'meson_exe.py custom'
+        else:
+            cmd_type = 'custom'
 
         elem.add_item('COMMAND', cmd)
-        elem.add_item('description', 'Generating %s with a custom command.' % target.name)
+        elem.add_item('description',  desc.format(target.name, cmd_type))
         elem.write(outfile)
         self.processed_targets[target.name + target.type_suffix()] = True