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Commit9bed827

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Fix configure's snprintf test so it exposes HP-UX bug.
Since commite1d19c9, buildfarm member gharial has been failing withsymptoms indicating that snprintf sometimes returns -1 for bufferoverrun, even though it passes the added configure check. Somegoogle research suggests that this happens only in limited cases,such as when the overrun happens partway through a %d item. Adjustthe configure check to exercise it that way. Since I'm now feelingmore paranoid than I was before, also make the test explicitly verifythat the buffer doesn't get physically overrun.
1 parentb94f7b5 commit9bed827

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2 files changed

+14
-6
lines changed

2 files changed

+14
-6
lines changed

‎config/c-library.m4

Lines changed: 8 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -202,7 +202,7 @@ AC_MSG_RESULT([$pgac_cv_snprintf_arg_control])
202202
])# PGAC_FUNC_SNPRINTF_ARG_CONTROL
203203

204204
# PGAC_FUNC_SNPRINTF_SIZE_T_SUPPORT
205-
# ---------------------------------------
205+
# ---------------------------------
206206
# Determine if snprintf supports the z length modifier for printing
207207
# size_t-sized variables. That's supported by C99 and POSIX but not
208208
# all platforms play ball, so we must test whether it's working.
@@ -243,9 +243,11 @@ AC_MSG_RESULT([$pgac_cv_snprintf_size_t_support])
243243
# Determine whether snprintf returns the desired buffer length when
244244
# it overruns the actual buffer length. That's required by C99 and POSIX
245245
# but ancient platforms don't behave that way, so we must test.
246+
# While we're at it, let's just verify that it doesn't physically overrun
247+
# the buffer.
246248
#
247249
AC_DEFUN([PGAC_FUNC_SNPRINTF_C99_RESULT],
248-
[AC_MSG_CHECKING([whether snprintfreports buffer overrun per C99])
250+
[AC_MSG_CHECKING([whether snprintfhandles buffer overrun per C99])
249251
AC_CACHE_VAL(pgac_cv_snprintf_c99_result,
250252
[AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <stdio.h>
251253
#include <string.h>
@@ -254,7 +256,10 @@ int main()
254256
{
255257
char buf[10];
256258
257-
if (snprintf(buf, sizeof(buf), "12345678901234567890") != 20)
259+
strcpy(buf, "abcdefghi");
260+
if (snprintf(buf, 4, "%d", 123456) != 6)
261+
return 1;
262+
if (strcmp(buf, "123") != 0 || buf[4] != 'e')
258263
return 1;
259264
return 0;
260265
}]])],

‎configure

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -16378,8 +16378,8 @@ fi
1637816378
# Force use of our snprintf if the system's doesn't handle buffer overrun
1637916379
# as specified by C99.
1638016380
if test "$pgac_need_repl_snprintf" = no; then
16381-
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether snprintfreports buffer overrun per C99" >&5
16382-
$as_echo_n "checking whether snprintfreports buffer overrun per C99... " >&6; }
16381+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether snprintfhandles buffer overrun per C99" >&5
16382+
$as_echo_n "checking whether snprintfhandles buffer overrun per C99... " >&6; }
1638316383
if ${pgac_cv_snprintf_c99_result+:} false; then :
1638416384
$as_echo_n "(cached) " >&6
1638516385
else
@@ -16395,7 +16395,10 @@ int main()
1639516395
{
1639616396
char buf[10];
1639716397

16398-
if (snprintf(buf, sizeof(buf), "12345678901234567890") != 20)
16398+
strcpy(buf, "abcdefghi");
16399+
if (snprintf(buf, 4, "%d", 123456) != 6)
16400+
return 1;
16401+
if (strcmp(buf, "123") != 0 || buf[4] != 'e')
1639916402
return 1;
1640016403
return 0;
1640116404
}

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