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Use libc_hidden_* for fputs (bug 15105)
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Tue, 13 Feb 2018 18:49:22 +0000
- Subject: Use libc_hidden_* for fputs (bug 15105)
- Authentication-results: sourceware.org; auth=none
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).
2018-02-13 Joseph Myers <joseph@codesourcery.com>
[BZ #15105]
* include/stdio.h [!_ISOMAC && IS_IN (libc)] (fputs): Use
libc_hidden_proto.
* libio/iofputs.c (fputs): Use libc_hidden_weak.
diff --git a/include/stdio.h b/include/stdio.h
index 94bc2fd..266c1d2 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -140,6 +140,10 @@ extern int _IO_new_fclose (_IO_FILE*);
# define fclose(fp) _IO_new_fclose (fp)
extern int _IO_fputs (const char*, _IO_FILE*);
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)
extern int _IO_new_fsetpos (_IO_FILE *, const _IO_fpos_t *);
# define fsetpos(fp, posp) _IO_new_fsetpos (fp, posp)
diff --git a/libio/iofputs.c b/libio/iofputs.c
index b4fbeb5..176e9ed 100644
--- a/libio/iofputs.c
+++ b/libio/iofputs.c
@@ -43,6 +43,7 @@ _IO_fputs (const char *str, _IO_FILE *fp)
libc_hidden_def (_IO_fputs)
weak_alias (_IO_fputs, fputs)
+libc_hidden_weak (fputs)
# ifndef _IO_MTSAFE_IO
strong_alias (_IO_fputs, __fputs_unlocked)
--
Joseph S. Myers
joseph@codesourcery.com