Fix detection of the result type of strerror_r().

The method we've traditionally used, of redeclaring strerror_r() to
see if the compiler complains of inconsistent declarations, turns out
not to work reliably because some compilers only report a warning,
not an error.  Amazingly, this has gone undetected for years, even
though it certainly breaks our detection of whether strerror_r
succeeded.

Let's instead test whether the compiler will take the result of
strerror_r() as a switch() argument.  It's possible this won't
work universally either, but it's the best idea I could come up with
on the spur of the moment.

Back-patch of commit 751f532b9.  Buildfarm results indicate that only
icc-on-Linux actually has an issue here; perhaps the lack of field
reports indicates that people don't build PG for production that way.

Discussion: https://postgr.es/m/[email protected]

4 files changed, 17 insertions, 18 deletions

diff --git a/config/c-library.m4 b/config/c-library.m4
index 70eb0e4dcf7..949f3a5e341 100644
--- a/config/c-library.m4
+++ b/config/c-library.m4
@@ -102,22 +102,23 @@ fi
 
 # PGAC_FUNC_STRERROR_R_INT
 # ---------------------------
-# Check if strerror_r() returns an int (SUSv3) rather than a char * (GNU libc)
-# If so, define STRERROR_R_INT
+# Check if strerror_r() returns int (POSIX) rather than char * (GNU libc).
+# If so, define STRERROR_R_INT.
+# The result is uncertain if strerror_r() isn't provided,
+# but we don't much care.
 AC_DEFUN([PGAC_FUNC_STRERROR_R_INT],
 [AC_CACHE_CHECK(whether strerror_r returns int,
 pgac_cv_func_strerror_r_int,
 [AC_TRY_COMPILE([#include <string.h>],
-[#ifndef _AIX
-int strerror_r(int, char *, size_t);
-#else
-/* Older AIX has 'int' for the third argument so we don't test the args. */
-int strerror_r();
-#endif],
+[char buf[100];
+  switch (strerror_r(1, buf, sizeof(buf)))
+  { case 0: break; default: break; }
+],
 [pgac_cv_func_strerror_r_int=yes],
 [pgac_cv_func_strerror_r_int=no])])
 if test x"$pgac_cv_func_strerror_r_int" = xyes ; then
-  AC_DEFINE(STRERROR_R_INT,, [Define to 1 if strerror_r() returns a int.])
+  AC_DEFINE(STRERROR_R_INT, 1,
+            [Define to 1 if strerror_r() returns int.])
 fi
 ])# PGAC_FUNC_STRERROR_R_INT
 
diff --git a/configure b/configure
index 7d111323960..5768f276a83 100755
--- a/configure
+++ b/configure
@@ -24978,12 +24978,10 @@ cat >>conftest.$ac_ext <<_ACEOF
 int
 main ()
 {
-#ifndef _AIX
-int strerror_r(int, char *, size_t);
-#else
-/* Older AIX has 'int' for the third argument so we don't test the args. */
-int strerror_r();
-#endif
+char buf[100];
+  switch (strerror_r(1, buf, sizeof(buf)))
+  { case 0: break; default: break; }
+
   ;
   return 0;
 }
@@ -25021,7 +25019,7 @@ $as_echo "$pgac_cv_func_strerror_r_int" >&6; }
 if test x"$pgac_cv_func_strerror_r_int" = xyes ; then
 
 cat >>confdefs.h <<\_ACEOF
-#define STRERROR_R_INT /**/
+#define STRERROR_R_INT 1
 _ACEOF
 
 fi
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 0121ea80281..3c553b4560f 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -773,7 +773,7 @@
 /* Define to 1 if you have the ANSI C header files. */
 #undef STDC_HEADERS
 
-/* Define to 1 if strerror_r() returns a int. */
+/* Define to 1 if strerror_r() returns int. */
 #undef STRERROR_R_INT
 
 /* Define to 1 if your <sys/time.h> declares `struct tm'. */
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index c287da32125..140912d71ba 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -633,7 +633,7 @@
 /* Define to 1 if you have the ANSI C header files. */
 #define STDC_HEADERS 1
 
-/* Define to 1 if strerror_r() returns a int. */
+/* Define to 1 if strerror_r() returns int. */
 /* #undef STRERROR_R_INT */
 
 /* Define to 1 if your <sys/time.h> declares `struct tm'. */