Try another way to detect the result type of strerror_r().

tglsfdc · tglsfdc · commit 751f532b9766 · 2018-09-26T18:23:13.000-04:00
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. We should probably back-patch this once the dust settles, but first let's see what the buildfarm thinks of it. Discussion: https://postgr.es/m/10877.1537993279@sss.pgh.pa.us
diff --git a/config/c-library.m4 b/config/c-library.m4
@@ -82,23 +82,23 @@ AH_VERBATIM(GETTIMEOFDAY_1ARG_,
 
 # 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_COMPILE_IFELSE([AC_LANG_PROGRAM([#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, 1,
-            [Define to 1 if strerror_r() returns a int.])
+            [Define to 1 if strerror_r() returns int.])
 fi
 ])# PGAC_FUNC_STRERROR_R_INT
 
diff --git a/configure b/configure
@@ -10792,12 +10792,10 @@ else
 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;
 }
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
@@ -852,7 +852,7 @@
 /* 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
@@ -665,7 +665,7 @@
 /* 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'. */

Original file line number	Diff line number	Diff line change
`@@ -10792,12 +10792,10 @@ else`
`10792`	`10792`	`int`
`10793`	`10793`	`main ()`
`10794`	`10794`	`{`
`10795`		`-#ifndef _AIX`
`10796`		`-int strerror_r(int, char *, size_t);`
`10797`		`-#else`
`10798`		`-/* Older AIX has 'int' for the third argument so we don't test the args. */`
`10799`		`-int strerror_r();`
`10800`		`-#endif`
	`10795`	`+char buf[100];`
	`10796`	`+ switch (strerror_r(1, buf, sizeof(buf)))`
	`10797`	`+ { case 0: break; default: break; }`
	`10798`	`+`
`10801`	`10799`	`;`
`10802`	`10800`	`return 0;`
`10803`	`10801`	`}`