From 5788052f3c6b2ac3d2bd761cbb333e50dad8670c Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 2 May 2014 15:30:35 -0400
Subject: [PATCH] Fix "quiet inline" configure test for newer clang compilers.
This test used to just define an unused static inline function and check
whether that causes a warning. But newer clang versions warn about
unused static inline functions when defined inside a .c file, but not
when defined in an included header, which is the case we care about.
Change the test to cope.
Andres Freund
---
config/c-compiler.m4 | 15 +++++++++++++--
config/test_quiet_include.h | 5 +++++
configure | 2 +-
3 files changed, 19 insertions(+), 3 deletions(-)
create mode 100644 config/test_quiet_include.h
diff --git a/config/c-compiler.m4 b/config/c-compiler.m4
index 9398ca6c477..8a216c9f73c 100644
--- a/config/c-compiler.m4
+++ b/config/c-compiler.m4
@@ -19,7 +19,18 @@ fi])# PGAC_C_SIGNED
# PGAC_C_INLINE
# -------------
-# Check if the C compiler understands inline functions.
+# Check if the C compiler understands inline functions without being
+# noisy about unused static inline functions. Some older compilers
+# understand inline functions (as tested by AC_C_INLINE) but warn about
+# them if they aren't used in a translation unit.
+#
+# This test used to just define an inline function, but some compilers
+# (notably clang) got too smart and now warn about unused static
+# inline functions when defined inside a .c file, but not when defined
+# in an included header. Since the latter is what we want to use, test
+# to see if the warning appears when the function is in a header file.
+# Not pretty, but it works.
+#
# Defines: inline, USE_INLINE
AC_DEFUN([PGAC_C_INLINE],
[AC_C_INLINE
@@ -28,7 +39,7 @@ AC_CACHE_CHECK([for quiet inline (no complaint if unreferenced)], pgac_cv_c_inli
if test "$ac_cv_c_inline" != no; then
pgac_c_inline_save_werror=$ac_c_werror_flag
ac_c_werror_flag=yes
- AC_LINK_IFELSE([AC_LANG_PROGRAM([static inline int fun () {return 0;}],[])],
+ AC_LINK_IFELSE([AC_LANG_PROGRAM([#include "$srcdir/config/test_quiet_include.h"],[])],
[pgac_cv_c_inline_quietly=yes])
ac_c_werror_flag=$pgac_c_inline_save_werror
fi])
diff --git a/config/test_quiet_include.h b/config/test_quiet_include.h
new file mode 100644
index 00000000000..eb0515ede78
--- /dev/null
+++ b/config/test_quiet_include.h
@@ -0,0 +1,5 @@
+/*
+ * For the raison d'etre of this file, check the comment above the definition
+ * of the PGAC_C_INLINE macro in config/c-compiler.m4.
+ */
+static inline int fun () { return 0; }
diff --git a/configure b/configure
index d9390d114f4..341eaab149c 100755
--- a/configure
+++ b/configure
@@ -15104,7 +15104,7 @@ _ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
-static inline int fun () {return 0;}
+#include "$srcdir/config/test_quiet_include.h"
int
main ()
{
--
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