Started work on MSVC precompiled headers. It does not work yet but I have been at it for so long that I want to just commit now because it at least does something close to the final result.

backends.py

@@ -112,6 +112,12 @@ class Backend():
         self.build_to_src = os.path.relpath(self.environment.get_source_dir(),
                                             self.environment.get_build_dir())
 
+    def get_compiler_for_lang(self, lang):
+        for i in self.build.compilers:
+            if i.language == lang:
+                return i
+        raise RuntimeError('No compiler for language ' + lang)
+
     def get_compiler_for_source(self, src):
         for i in self.build.compilers:
             if i.can_compile(src):
@@ -171,10 +177,13 @@ class Backend():
         args = []
         pchpath = self.get_target_private_dir(target)
         includearg = compiler.get_include_arg(pchpath)
-        for p in target.get_pch():
-            if compiler.can_compile(p):
+        for lang in ['c', 'cpp']:
+            p = target.get_pch(lang)
+            if len(p) == 0:
+                continue
+            if compiler.can_compile(p[-1]):
                 args.append('-include')
-                args.append(os.path.split(p)[-1])
+                args.append(os.path.split(p[0])[-1])
         if len(args) > 0:
             args = [includearg] + args
         return args
@@ -595,7 +604,7 @@ class NinjaBackend(Backend):
         rel_obj = os.path.join(self.get_target_private_dir(target), os.path.basename(src_filename))
         rel_obj += '.' + self.environment.get_object_suffix()
         dep_file = rel_obj + '.' + compiler.get_depfile_suffix()
-        pchlist = target.get_pch()
+        pchlist = target.get_pch(compiler.language)
         if len(pchlist) == 0:
             pch_dep = []
         else:
@@ -628,22 +637,54 @@ class NinjaBackend(Backend):
         element.write(outfile)
         return rel_obj
 
+    def generate_msvc_pch_command(self, target, compiler, pch):
+        if len(pch) != 2:
+            raise RuntimeError('MSVC requires one header and one source to produce precompiled headers.')
+        header = pch[0]
+        source = pch[1]
+        chopped = os.path.split(header)[-1].split('.')[:-1]
+        chopped.append(compiler.get_pch_suffix())
+        pchname = '.'.join(chopped)
+        dst = os.path.join(self.get_target_private_dir(target), pchname)
+
+        commands = []
+        commands += self.generate_basic_compiler_flags(target, compiler)
+        commands += compiler.gen_pch_args(header, source, dst)
+        
+        dep = dst + '.' + compiler.get_depfile_suffix()
+        return (commands, dep, dst)
+
+    def generate_gcc_pch_command(self, target, compiler, pch):
+        commands = []
+        commands += self.generate_basic_compiler_flags(target, compiler)
+        
+        dst = os.path.join(self.get_target_private_dir(target),
+                           os.path.split(pch)[-1] + '.' + compiler.get_pch_suffix())
+        dep = dst + '.' + compiler.get_depfile_suffix()
+        return (commands, dep, dst)
+
     def generate_pch(self, target, outfile):
-        for pch in target.get_pch():
-            if '/' not in pch:
+        for lang in ['c', 'cpp']:
+            pch = target.get_pch(lang)
+            if len(pch) == 0:
+                continue
+            if '/' not in pch[0] or '/' not in pch[-1]:
                 raise interpreter.InvalidArguments('Precompiled header of "%s" must not be in the same direcotory as source, please put it in a subdirectory.' % target.get_basename())
-            compiler = self.get_compiler_for_source(pch)
-            commands = []
-            commands += self.generate_basic_compiler_flags(target, compiler)
-            src = os.path.join(self.build_to_src, target.get_source_subdir(), pch)
-            dst = os.path.join(self.get_target_private_dir(target),
-                                  os.path.split(pch)[-1] + '.' + compiler.get_pch_suffix())
-            dep = dst + '.' + compiler.get_depfile_suffix()
+            compiler = self.get_compiler_for_lang(lang)
+            src = os.path.join(self.build_to_src, target.get_source_subdir(), pch[-1])
+            if compiler.id == 'msvc':
+                (commands, dep, dst) = self.generate_msvc_pch_command(target, compiler, pch)
+                extradep = os.path.join(self.build_to_src, target.get_source_subdir(), pch[0])
+            else:
+                (commands, dep, dst) = self.generate_gcc_pch_command(target, compiler, pch[0])
+                extradep = None
             elem = NinjaBuildElement(dst, compiler.get_language() + '_COMPILER', src)
+            if extradep is not None:
+                elem.add_dep(extradep)
             elem.add_item('FLAGS', commands)
             elem.add_item('DEPFILE', dep)
             elem.write(outfile)
-            
+
     def generate_shsym(self, outfile, target):
         target_name = self.get_target_filename(target)
         targetdir = self.get_target_private_dir(target)

environment.py

@@ -169,8 +169,6 @@ int main(int argc, char **argv) {
             raise EnvironmentException('Could not run sizeof test binary.')
         return int(so.decode())
 
-cpp_suffixes = ['cc', 'cpp', 'cxx', 'hh', 'hpp', 'hxx']
-
 class CPPCompiler(CCompiler):
     def __init__(self, exelist):
         CCompiler.__init__(self, exelist)
@@ -280,6 +278,9 @@ class VisualStudioCCompiler(CCompiler):
     def get_std_shared_lib_link_flags(self):
         return ['/DLL']
 
+    def gen_pch_args(self, header, source, pchname):
+        return ['/Yc' + header, '/Fp' + pchname]
+
     def sanity_check(self, work_dir):
         source_name = os.path.join(work_dir, 'sanitycheckc.c')
         binary_name = os.path.join(work_dir, 'sanitycheckc')
@@ -504,6 +505,17 @@ def is_windows():
     return platform.system().lower() == 'windows'
 
 header_suffixes = ['h', 'hh', 'hpp', 'hxx', 'H']
+cpp_suffixes = ['cc', 'cpp', 'cxx', 'hh', 'hpp', 'hxx']
+c_suffixes = ['c']
+clike_suffixes = c_suffixes + cpp_suffixes
+
+def is_header(fname):
+    suffix = fname.split('.')[-1]
+    return suffix in header_suffixes
+
+def is_source(fname):
+    suffix = fname.split('.')[-1]
+    return suffix in clike_suffixes
 
 class Environment():
     private_dir = 'meson-private'
@@ -573,8 +585,10 @@ class Environment():
         return self.meson_script_file
 
     def is_header(self, fname):
-        suffix = fname.split('.')[-1]
-        return suffix in header_suffixes
+        return is_header(fname)
+    
+    def is_source(self, fname):
+        return is_source(fname)
 
     def detect_c_compiler(self):
         evar = 'CC'

interpreter.py

@@ -348,7 +348,7 @@ class BuildTarget(InterpreterObject):
         self.link_targets = []
         self.filename = 'no_name'
         self.need_install = False
-        self.pch = []
+        self.pch = {}
         self.extra_args = {}
         self.generated = []
         self.process_sourcelist(sources)
@@ -379,10 +379,14 @@ class BuildTarget(InterpreterObject):
             llist = [llist]
         for linktarget in llist:
             self.link(linktarget)
-        pchlist = kwargs.get('pch', [])
-        if not isinstance(pchlist, list):
-            pchlist = [pchlist]
-        self.add_pch(pchlist)
+        c_pchlist = kwargs.get('c_pch', [])
+        if not isinstance(c_pchlist, list):
+            c_pchlist = [c_pchlist]
+        self.add_pch('c', c_pchlist)
+        cpp_pchlist = kwargs.get('cpp_pch', [])
+        if not isinstance(cpp_pchlist, list):
+            cpp_pchlist = [cpp_pchlist]
+        self.add_pch('cpp', cpp_pchlist)
         clist = kwargs.get('c_args', [])
         if not isinstance(clist, list):
             clist = [clist]
@@ -434,8 +438,11 @@ class BuildTarget(InterpreterObject):
     def has_pch(self):
         return len(self.pch) > 0
 
-    def get_pch(self):
-        return self.pch
+    def get_pch(self, language):
+        try:
+            return self.pch[language]
+        except KeyError:
+            return[]
 
     def get_include_dirs(self):
         return self.include_dirs
@@ -467,9 +474,20 @@ class BuildTarget(InterpreterObject):
                 raise InvalidArguments('Generated source argument is not the output of a generator.')
             self.generated.append(g)
 
-    def add_pch(self, pchlist):
-        for a in pchlist:
-            self.pch.append(a)
+    def add_pch(self, language, pchlist):
+        if len(pchlist) == 0:
+            return
+        if len(pchlist) == 2:
+            if environment.is_header(pchlist[0]):
+                if not environment.is_source(pchlist[1]):
+                    raise InterpreterException('PCH definition must contain one header and at most one source.')
+            elif environment.is_source(pchlist[0]):
+                if not environment.is_header(pchlist[1]):
+                    raise InterpreterException('PCH definition must contain one header and at most one source.')
+            pchlist = [pchlist[1], pchlist[0]]
+        elif len(pchlist) > 2:
+            raise InterpreterException('PCH definition may have a maximum of 2 files.')
+        self.pch[language] = pchlist
 
     def add_include_dirs(self, args):
         for a in args:

test cases/common/13 pch/meson.build

@@ -1,3 +1,4 @@
 project('pch test', 'c')
 
-exe = executable('prog', 'prog.c', pch : 'pch/prog.h')
+exe = executable('prog', 'prog.c',
+c_pch : ['pch/prog_pch.c', 'pch/prog.h'])

test cases/common/13 pch/prog.c

@@ -1,3 +1,7 @@
+#if defined(_MSC_VER)
+#include"prog.pch"
+#endif
+
 void func() {
     fprintf(stdout, "This is a function that fails if stdio is not #included.\n");
 }