Require a C99-compliant snprintf(), and remove related workarounds.

Since our substitute snprintf now returns a C99-compliant result,
there's no need anymore to have complicated code to cope with pre-C99
behavior.  We can just make configure substitute snprintf.c if it finds
that the system snprintf() is pre-C99.  (Note: I do not believe that
there are any platforms where this test will trigger that weren't
already being rejected due to our other C99-ish feature requirements for
snprintf.  But let's add the check for paranoia's sake.)  Then, simplify
the call sites that had logic to cope with the pre-C99 definition.

I also dropped some stuff that was being paranoid about the possibility
of snprintf overrunning the given buffer.  The only reports we've ever
heard of that being a problem were for Solaris 7, which is long dead,
and we've sure not heard any reports of these assertions triggering in
a long time.  So let's drop that complexity too.

Likewise, drop some code that wasn't trusting snprintf to set errno
when it returns -1.  That would be not-per-spec, and again there's
no real reason to believe it is a live issue, especially not for
snprintfs that pass all of configure's feature checks.

Discussion: https://postgr.es/m/17245.1534289329@sss.pgh.pa.us

1 files changed, 45 insertions, 1 deletions

diff --git a/configure b/configure
index 1aaca9ab5c..a2374a3ab6 100755
--- a/configure
+++ b/configure
@@ -16142,7 +16142,7 @@ fi
 # Run tests below here
 # --------------------
 
-# Force use of our snprintf if system's doesn't do arg control
+# For NLS, force use of our snprintf if system's doesn't do arg control.
 # See comment above at snprintf test for details.
 if test "$enable_nls" = yes -a "$pgac_need_repl_snprintf" = no; then
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether snprintf supports argument control" >&5
@@ -16436,6 +16436,50 @@ $as_echo "$pgac_cv_snprintf_size_t_support" >&6; }
   fi
 fi
 
+# Force use of our snprintf if the system's doesn't handle buffer overrun
+# as specified by C99.
+if test "$pgac_need_repl_snprintf" = no; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether snprintf reports buffer overrun per C99" >&5
+$as_echo_n "checking whether snprintf reports buffer overrun per C99... " >&6; }
+if ${pgac_cv_snprintf_c99_result+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test "$cross_compiling" = yes; then :
+  pgac_cv_snprintf_c99_result=cross
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <stdio.h>
+#include <string.h>
+
+int main()
+{
+  char buf[10];
+
+  if (snprintf(buf, sizeof(buf), "12345678901234567890") != 20)
+    return 1;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_run "$LINENO"; then :
+  pgac_cv_snprintf_c99_result=yes
+else
+  pgac_cv_snprintf_c99_result=no
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_snprintf_c99_result" >&5
+$as_echo "$pgac_cv_snprintf_c99_result" >&6; }
+
+  if test "$pgac_cv_snprintf_c99_result" != yes; then
+    pgac_need_repl_snprintf=yes
+  fi
+fi
+
 # Now we have checked all the reasons to replace snprintf
 if test $pgac_need_repl_snprintf = yes; then