From f1b32aa4bbf7091719b83e64febc1a9f2f4ed67d Mon Sep 17 00:00:00 2001
From: Nicolas Schneider <nioncode+git@gmail.com>
Date: Tue, 1 Jan 2019 11:50:16 +0100
Subject: [PATCH] vs: respect 'b_pch' option

Fixes #4681.
---
 mesonbuild/backend/vs2010backend.py           | 29 ++++++++++---------
 .../3 pch disabled/c/meson.build              |  2 ++
 .../failing build/3 pch disabled/c/pch/prog.h |  1 +
 .../3 pch disabled/c/pch/prog_pch.c           |  5 ++++
 .../failing build/3 pch disabled/c/prog.c     | 10 +++++++
 .../failing build/3 pch disabled/meson.build  |  5 ++++
 6 files changed, 38 insertions(+), 14 deletions(-)
 create mode 100644 test cases/failing build/3 pch disabled/c/meson.build
 create mode 100644 test cases/failing build/3 pch disabled/c/pch/prog.h
 create mode 100644 test cases/failing build/3 pch disabled/c/pch/prog_pch.c
 create mode 100644 test cases/failing build/3 pch disabled/c/prog.c
 create mode 100644 test cases/failing build/3 pch disabled/meson.build

diff --git a/mesonbuild/backend/vs2010backend.py b/mesonbuild/backend/vs2010backend.py
index 8ac88cec6..939f7b44f 100644
--- a/mesonbuild/backend/vs2010backend.py
+++ b/mesonbuild/backend/vs2010backend.py
@@ -982,7 +982,6 @@ class Vs2010Backend(backends.Backend):
         target_defines.append('%(PreprocessorDefinitions)')
         ET.SubElement(clconf, 'PreprocessorDefinitions').text = ';'.join(target_defines)
         ET.SubElement(clconf, 'FunctionLevelLinking').text = 'true'
-        pch_node = ET.SubElement(clconf, 'PrecompiledHeader')
         # Warning level
         warning_level = self.get_option_for_target('warning_level', target)
         ET.SubElement(clconf, 'WarningLevel').text = 'Level' + str(1 + int(warning_level))
@@ -990,19 +989,21 @@ class Vs2010Backend(backends.Backend):
             ET.SubElement(clconf, 'TreatWarningAsError').text = 'true'
         # Note: SuppressStartupBanner is /NOLOGO and is 'true' by default
         pch_sources = {}
-        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) != 2:
-                    raise MesonException('MSVC requires one header and one source to produce precompiled headers.')
-                pch_sources[lang] = [pch[0], pch[1], lang]
-            else:
-                # 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]
+        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) != 2:
+                        raise MesonException('MSVC requires one header and one source to produce precompiled headers.')
+                    pch_sources[lang] = [pch[0], pch[1], lang]
+                else:
+                    # 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]
         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.
diff --git a/test cases/failing build/3 pch disabled/c/meson.build b/test cases/failing build/3 pch disabled/c/meson.build
new file mode 100644
index 000000000..1739126df
--- /dev/null
+++ b/test cases/failing build/3 pch disabled/c/meson.build	
@@ -0,0 +1,2 @@
+exe = executable('prog', 'prog.c',
+c_pch : ['pch/prog_pch.c', 'pch/prog.h'])
diff --git a/test cases/failing build/3 pch disabled/c/pch/prog.h b/test cases/failing build/3 pch disabled/c/pch/prog.h
new file mode 100644
index 000000000..354499acd
--- /dev/null
+++ b/test cases/failing build/3 pch disabled/c/pch/prog.h	
@@ -0,0 +1 @@
+#include<stdio.h>
diff --git a/test cases/failing build/3 pch disabled/c/pch/prog_pch.c b/test cases/failing build/3 pch disabled/c/pch/prog_pch.c
new file mode 100644
index 000000000..49605057b
--- /dev/null
+++ b/test cases/failing build/3 pch disabled/c/pch/prog_pch.c	
@@ -0,0 +1,5 @@
+#if !defined(_MSC_VER)
+#error "This file is only for use with MSVC."
+#endif
+
+#include "prog.h"
diff --git a/test cases/failing build/3 pch disabled/c/prog.c b/test cases/failing build/3 pch disabled/c/prog.c
new file mode 100644
index 000000000..0ce3d0a24
--- /dev/null
+++ b/test cases/failing build/3 pch disabled/c/prog.c	
@@ -0,0 +1,10 @@
+// No includes here, they need to come from the PCH
+
+void func() {
+    fprintf(stdout, "This is a function that fails if stdio is not #included.\n");
+}
+
+int main(int argc, char **argv) {
+    return 0;
+}
+
diff --git a/test cases/failing build/3 pch disabled/meson.build b/test cases/failing build/3 pch disabled/meson.build
new file mode 100644
index 000000000..0a8fa6793
--- /dev/null
+++ b/test cases/failing build/3 pch disabled/meson.build	
@@ -0,0 +1,5 @@
+# Disable PCH usage to make sure backends respect this setting.
+# Since the .c file requires PCH usage (it does not include necessary
+# headers itself), the build should fail.
+project('pch test', 'c', default_options: ['b_pch=false'])
+subdir('c')