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Fix configure's snprintf test so it exposes HP-UX bug.

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Since commit e1d19c902, buildfarm member gharial has been failing with
symptoms indicating that snprintf sometimes returns -1 for buffer
overrun, even though it passes the added configure check.  Some
google research suggests that this happens only in limited cases,
such as when the overrun happens partway through a %d item.  Adjust
the configure check to exercise it that way.  Since I'm now feeling
more paranoid than I was before, also make the test explicitly verify
that the buffer doesn't get physically overrun.
This commit is contained in:
Tom Lane 2018-08-17 10:37:59 -04:00
parent b94f7b5350
commit 9bed827b18
2 changed files with 14 additions and 6 deletions
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11
config/c-library.m4
View File

@ -202,7 +202,7 @@ AC_MSG_RESULT([$pgac_cv_snprintf_arg_control])
])# PGAC_FUNC_SNPRINTF_ARG_CONTROL
# PGAC_FUNC_SNPRINTF_SIZE_T_SUPPORT
# ---------------------------------------
# ---------------------------------
# Determine if snprintf supports the z length modifier for printing
# size_t-sized variables. That's supported by C99 and POSIX but not
# all platforms play ball, so we must test whether it's working.
@ -243,9 +243,11 @@ AC_MSG_RESULT([$pgac_cv_snprintf_size_t_support])
# Determine whether snprintf returns the desired buffer length when
# it overruns the actual buffer length. That's required by C99 and POSIX
# but ancient platforms don't behave that way, so we must test.
# While we're at it, let's just verify that it doesn't physically overrun
# the buffer.
#
AC_DEFUN([PGAC_FUNC_SNPRINTF_C99_RESULT],
[AC_MSG_CHECKING([whether snprintf reports buffer overrun per C99])
[AC_MSG_CHECKING([whether snprintf handles buffer overrun per C99])
AC_CACHE_VAL(pgac_cv_snprintf_c99_result,
[AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <stdio.h>
#include <string.h>
@ -254,7 +256,10 @@ int main()
{
char buf[10];
if (snprintf(buf, sizeof(buf), "12345678901234567890") != 20)
strcpy(buf, "abcdefghi");
if (snprintf(buf, 4, "%d", 123456) != 6)
return 1;
if (strcmp(buf, "123") != 0 || buf[4] != 'e')
return 1;
return 0;
}]])],

9
configure vendored
View File

@ -16378,8 +16378,8 @@ 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; }
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether snprintf handles buffer overrun per C99" >&5
$as_echo_n "checking whether snprintf handles buffer overrun per C99... " >&6; }
if ${pgac_cv_snprintf_c99_result+:} false; then :
$as_echo_n "(cached) " >&6
else
@ -16395,7 +16395,10 @@ int main()
{
char buf[10];
if (snprintf(buf, sizeof(buf), "12345678901234567890") != 20)
strcpy(buf, "abcdefghi");
if (snprintf(buf, 4, "%d", 123456) != 6)
return 1;
if (strcmp(buf, "123") != 0 || buf[4] != 'e')
return 1;
return 0;
}