backend/vs: Fix build when not all languages have pch

It is not unheard-of for a project to use pch for C++ but not for C
(because C usually builds fast enough anyway, so it's not worth the
developer overhead of maintaining the pch file).

This code was trying to optimize the vcxproj file size by detecting
"only one language", but it was only looking at the number of
pch-languages defined. This is incorrect when pch is not defined for all
languages in use.

Instead of tweaking the optimization further, remove it. This makes the
vs backend behave more like the ninja backend.

1 files changed, 4 insertions, 10 deletions

diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index ef849e1..80ff910 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -591,10 +591,8 @@ class Vs2010Backend(backends.Backend):
         raise MesonException('Could not guess language from source file %s.' % src)
 
     def add_pch(self, pch_sources, lang, inc_cl):
-        if len(pch_sources) <= 1:
-            # We only need per file precompiled headers if we have more than 1 language.
-            return
-        self.use_pch(pch_sources, lang, inc_cl)
+        if lang in pch_sources:
+            self.use_pch(pch_sources, lang, inc_cl)
 
     def create_pch(self, pch_sources, lang, inc_cl):
         pch = ET.SubElement(inc_cl, 'PrecompiledHeader')
@@ -602,6 +600,8 @@ class Vs2010Backend(backends.Backend):
         self.add_pch_files(pch_sources, lang, inc_cl)
 
     def use_pch(self, pch_sources, lang, inc_cl):
+        pch = ET.SubElement(inc_cl, 'PrecompiledHeader')
+        pch.text = 'Use'
         header = self.add_pch_files(pch_sources, lang, inc_cl)
         pch_include = ET.SubElement(inc_cl, 'ForcedIncludeFiles')
         pch_include.text = header + ';%(ForcedIncludeFiles)'
@@ -1046,12 +1046,10 @@ class Vs2010Backend(backends.Backend):
         # Note: SuppressStartupBanner is /NOLOGO and is 'true' by default
         pch_sources = {}
         if self.environment.coredata.base_options.get('b_pch', False):
-            pch_node = ET.SubElement(clconf, 'PrecompiledHeader')
             for lang in ['c', 'cpp']:
                 pch = target.get_pch(lang)
                 if not pch:
                     continue
-                pch_node.text = 'Use'
                 if compiler.id == 'msvc':
                     if len(pch) == 1:
                         # Auto generate PCH.
@@ -1065,10 +1063,6 @@ class Vs2010Backend(backends.Backend):
                     # I don't know whether its relevant but let's handle other compilers
                     # used with a vs backend
                     pch_sources[lang] = [pch[0], None, lang, None]
-        if len(pch_sources) == 1:
-            # If there is only 1 language with precompiled headers, we can use it for the entire project, which
-            # is cleaner than specifying it for each source file.
-            self.use_pch(pch_sources, list(pch_sources)[0], clconf)
 
         resourcecompile = ET.SubElement(compiles, 'ResourceCompile')
         ET.SubElement(resourcecompile, 'PreprocessorDefinitions')