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

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')

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
 

mesonbuild/mesonmain.py

@@ -163,7 +163,10 @@ itself as required.'''
 def run_script_command(args):
     cmdname = args[0]
     cmdargs = args[1:]
-    if cmdname == 'test':
+    if cmdname == 'exe':
+        import mesonbuild.scripts.meson_exe as abc
+        cmdfunc = abc.run
+    elif cmdname == 'test':
         import mesonbuild.scripts.meson_test as abc
         cmdfunc = abc.run
     elif cmdname == 'benchmark':

mesonbuild/scripts/meson_exe.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+
+# Copyright 2013-2016 The Meson development team
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import sys
+import argparse
+import pickle
+import platform
+import subprocess
+
+import mesonbuild
+
+options = None
+
+parser = argparse.ArgumentParser()
+parser.add_argument('args', nargs='+')
+
+def is_windows():
+    platname = platform.system().lower()
+    return platname == 'windows' or 'mingw' in platname
+
+def run_with_mono(fname):
+    if fname.endswith('.exe') and not is_windows():
+        return True
+    return False
+
+def run_exe(exe):
+    if exe.fname[0].endswith('.jar'):
+        cmd = ['java', '-jar'] + exe.fname
+    elif not exe.is_cross and run_with_mono(exe.fname[0]):
+        cmd = ['mono'] + exe.fname
+    else:
+        if exe.is_cross:
+            if exe.exe_runner is None:
+                raise Exception('BUG: Trying to run cross-compiled exes with no wrapper')
+            else:
+                cmd = [exe.exe_runner] + exe.fname
+        else:
+            cmd = exe.fname
+    child_env = os.environ.copy()
+    child_env.update(exe.env)
+    if len(exe.extra_paths) > 0:
+        child_env['PATH'] = child_env['PATH'] + ';'.join([''] + exe.extra_paths)
+    p = subprocess.Popen(cmd + exe.cmd_args,
+                         stdout=subprocess.PIPE,
+                         stderr=subprocess.PIPE,
+                         env=child_env,
+                         cwd=exe.workdir)
+
+def run(args):
+    global options
+    options = parser.parse_args(args)
+    if len(options.args) != 1:
+        print('Test runner for Meson. Do not run on your own, mmm\'kay?')
+        print(sys.argv[0] + ' [data file]')
+    exe_data_file = options.args[0]
+    exe = pickle.load(open(exe_data_file, 'rb'))
+    run_exe(exe)
+
+if __name__ == '__main__':
+    sys.exit(run(sys.argv[1:]))