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Fix strftime build with GCC 8.

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Building with current GCC mainline fails with:

strftime_l.c: In function '__strftime_internal':
strftime_l.c:719:4: error: macro expands to multiple statements [-Werror=multistatement-macros]
    digits = d > width ? d : width;          \
    ^
strftime_l.c:1260:6: note: in expansion of macro 'DO_NUMBER'
      DO_NUMBER (1, tp->tm_year + TM_YEAR_BASE);
      ^~~~~~~~~
strftime_l.c:1259:4: note: some parts of macro expansion are not guarded by this 'else' clause
    else
    ^~~~

In fact this particular instance is harmless; the code looks like:

          if (modifier == L_('O'))
            goto bad_format;
          else
            DO_NUMBER (1, tp->tm_year + TM_YEAR_BASE);

and because of the goto, it doesn't matter that part of the expansion
isn't under the "else" conditional.  But it's also clearly bad style
to rely on that.  This patch changes DO_NUMBER and DO_NUMBER_SPACEPAD
to use do { } while (0) to avoid such problems.

Tested (full testsuite) for x86_64 (GCC 6), and with
build-many-glibcs.py with GCC mainline, in conjunction with my libgcc
patch <https://gcc.gnu.org/ml/gcc-patches/2017-06/msg02032.html>.

	* time/strftime_l.c (DO_NUMBER): Define using do { } while (0).
	(DO_NUMBER_SPACEPAD): Likewise.
This commit is contained in:
Joseph Myers 2017-06-27 17:12:13 +00:00
parent f8f72bc0c3
commit e4043b84c4
2 changed files with 21 additions and 6 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2017-06-27 Joseph Myers <joseph@codesourcery.com>
* time/strftime_l.c (DO_NUMBER): Define using do { } while (0).
(DO_NUMBER_SPACEPAD): Likewise.
2017-06-27 Prakhar Bahuguna <prakhar.bahuguna@arm.com>
* sysdeps/arm/armv7/multiarch/Makefile: Add memchr_neon to

22
time/strftime_l.c
View File

@ -715,12 +715,22 @@ __strftime_internal (CHAR_T *s, size_t maxsize, const CHAR_T *format,
format_char = *f;
switch (format_char)
{
#define DO_NUMBER(d, v) \
digits = d > width ? d : width; \
number_value = v; goto do_number
#define DO_NUMBER_SPACEPAD(d, v) \
digits = d > width ? d : width; \
number_value = v; goto do_number_spacepad
#define DO_NUMBER(d, v) \
do \
{ \
digits = d > width ? d : width; \
number_value = v; \
goto do_number; \
} \
while (0)
#define DO_NUMBER_SPACEPAD(d, v) \
do \
{ \
digits = d > width ? d : width; \
number_value = v; \
goto do_number_spacepad; \
} \
while (0)
case L_('%'):
if (modifier != 0)