From 505c9544247f27cb6ebf749d0902d53c33dac308 Mon Sep 17 00:00:00 2001
From: Philip Withnall <withnall@endlessm.com>
Date: Mon, 28 Oct 2019 17:05:46 +0000
Subject: [PATCH] build: Check size_t compatibility with various other types

When choosing the type to base `size_t` on, check the compatibility of
passing pointers, as well as the width of the type, to avoid compiler
warnings in future.

For now, the code to do the checks is fairly ugly due to limitations in
Meson. In particular, the new checks are limited to gcc and clang (other
compilers will behave as before), and they are all duplicated. See the
comments in the code for links to Meson improvement requests.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Fixes: #1777
---
 meson.build | 66 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 62 insertions(+), 4 deletions(-)

diff --git a/meson.build b/meson.build
index 04ca06392..8638f0133 100644
--- a/meson.build
+++ b/meson.build
@@ -1320,28 +1320,86 @@ else
   glibconfig_conf.set('g_searchpath_separator', ':')
 endif
 
-if sizet_size == short_size
+g_sizet_compatibility = {
+  'short': sizet_size == short_size,
+  'int': sizet_size == int_size,
+  'long': sizet_size == long_size,
+  'long long': sizet_size == long_long_size,
+}
+
+# Do separate checks for gcc/clang (and ignore other compilers for now), since
+# we need to explicitly pass -Werror to the compilers.
+# FIXME: https://github.com/mesonbuild/meson/issues/5399
+# We can’t simplify these checks using a foreach loop because dictionary keys
+# have to be string literals.
+# FIXME: https://github.com/mesonbuild/meson/issues/5231
+if cc.get_id() == 'gcc' or cc.get_id() == 'clang'
+  g_sizet_compatibility += {
+    'short': g_sizet_compatibility['short'] and cc.compiles(
+        '''#include <stddef.h>
+        size_t f (size_t *i) { return *i + 1; }
+        int main (void) {
+          unsigned short i = 0;
+          f (&i);
+          return 0;
+        }''',
+        args: ['-Werror'],
+        name : 'GCC size_t typedef is short'),
+    'int': g_sizet_compatibility['int'] and cc.compiles(
+        '''#include <stddef.h>
+        size_t f (size_t *i) { return *i + 1; }
+        int main (void) {
+          unsigned int i = 0;
+          f (&i);
+          return 0;
+        }''',
+        args: ['-Werror'],
+        name : 'GCC size_t typedef is int'),
+    'long': g_sizet_compatibility['long'] and cc.compiles(
+        '''#include <stddef.h>
+        size_t f (size_t *i) { return *i + 1; }
+        int main (void) {
+          unsigned long i = 0;
+          f (&i);
+          return 0;
+        }''',
+        args: ['-Werror'],
+        name : 'GCC size_t typedef is long'),
+    'long long': g_sizet_compatibility['long long'] and cc.compiles(
+        '''#include <stddef.h>
+        size_t f (size_t *i) { return *i + 1; }
+        int main (void) {
+          unsigned long long i = 0;
+          f (&i);
+          return 0;
+        }''',
+        args: ['-Werror'],
+        name : 'GCC size_t typedef is long long'),
+  }
+endif
+
+if g_sizet_compatibility['short']
   glibconfig_conf.set('glib_size_type_define', 'short')
   glibconfig_conf.set_quoted('gsize_modifier', 'h')
   glibconfig_conf.set_quoted('gssize_modifier', 'h')
   glibconfig_conf.set_quoted('gsize_format', 'hu')
   glibconfig_conf.set_quoted('gssize_format', 'hi')
   glibconfig_conf.set('glib_msize_type', 'SHRT')
-elif sizet_size == int_size
+elif g_sizet_compatibility['int']
   glibconfig_conf.set('glib_size_type_define', 'int')
   glibconfig_conf.set_quoted('gsize_modifier', '')
   glibconfig_conf.set_quoted('gssize_modifier', '')
   glibconfig_conf.set_quoted('gsize_format', 'u')
   glibconfig_conf.set_quoted('gssize_format', 'i')
   glibconfig_conf.set('glib_msize_type', 'INT')
-elif sizet_size == long_size
+elif g_sizet_compatibility['long']
   glibconfig_conf.set('glib_size_type_define', 'long')
   glibconfig_conf.set_quoted('gsize_modifier', 'l')
   glibconfig_conf.set_quoted('gssize_modifier', 'l')
   glibconfig_conf.set_quoted('gsize_format', 'lu')
   glibconfig_conf.set_quoted('gssize_format', 'li')
   glibconfig_conf.set('glib_msize_type', 'LONG')
-elif sizet_size == long_long_size
+elif g_sizet_compatibility['long long']
   glibconfig_conf.set('glib_size_type_define', 'long long')
   glibconfig_conf.set_quoted('gsize_modifier', int64_m)
   glibconfig_conf.set_quoted('gssize_modifier', int64_m)