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Use libc_hidden_* for fputs (bug 15105).

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Among other localplt test failures when building with -Os, there are
libc.so PLT references for fputs.  fputs calls normally get redirected
to _IO_fputs by a macro in include/stdio.h (and _IO_fputs in turn uses
libc_hidden_proto), but GCC can convert an fprintf call with a
constant string argument into an fputs call, which of course is then
unaffected by the macro redirection.  (I don't know why this issue
only appears with -Os.)

This patch duly adds a use of libc_hidden_proto for fputs.  I see no
obvious reason why the fputs macro redirection is needed at all, but
this patch does not change it.

Tested for x86_64 (both that it removes this particular localplt
failure for -Os - but other such failures remain so the bug can't yet
be closed - and that the testsuite continues to pass without -Os).

	[BZ #15105]
	* include/stdio.h [!_ISOMAC && IS_IN (libc)] (fputs): Use
	libc_hidden_proto.
	* libio/iofputs.c (fputs): Use libc_hidden_weak.

(cherry picked from commit 499b315324)
This commit is contained in:
Joseph Myers 2018-02-15 20:58:16 +00:00 committed by Fangrui Song
parent aac0d8a9a3
commit d7c1214f4d
2 changed files with 5 additions and 0 deletions
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4
include/stdio.h
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@ -135,6 +135,10 @@ extern int _IO_new_fclose (_IO_FILE*);
# define fclose(fp) _IO_new_fclose (fp) # define fclose(fp) _IO_new_fclose (fp)
extern int _IO_fputs (const char*, _IO_FILE*); extern int _IO_fputs (const char*, _IO_FILE*);
libc_hidden_proto (_IO_fputs) libc_hidden_proto (_IO_fputs)
/* The compiler may optimize calls to fprintf into calls to fputs.
Use libc_hidden_proto to ensure that those calls, not redirected by
the fputs macro, also do not go through the PLT. */
libc_hidden_proto (fputs)
# define fputs(str, fp) _IO_fputs (str, fp) # define fputs(str, fp) _IO_fputs (str, fp)
extern int _IO_new_fsetpos (_IO_FILE *, const _IO_fpos_t *); extern int _IO_new_fsetpos (_IO_FILE *, const _IO_fpos_t *);
# define fsetpos(fp, posp) _IO_new_fsetpos (fp, posp) # define fsetpos(fp, posp) _IO_new_fsetpos (fp, posp)

1
libio/iofputs.c
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@ -43,6 +43,7 @@ _IO_fputs (const char *str, _IO_FILE *fp)
libc_hidden_def (_IO_fputs) libc_hidden_def (_IO_fputs)
weak_alias (_IO_fputs, fputs) weak_alias (_IO_fputs, fputs)
libc_hidden_weak (fputs)
# ifndef _IO_MTSAFE_IO # ifndef _IO_MTSAFE_IO
strong_alias (_IO_fputs, __fputs_unlocked) strong_alias (_IO_fputs, __fputs_unlocked)