[glibc/google/grte/v5-2.27/master] Use libc_hidden_* for fputs (bug 15105).

[Fangrui Song <maskray@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b8365ac9056e572ef9cbf1e40a2691b7e06f1f2e

commit b8365ac9056e572ef9cbf1e40a2691b7e06f1f2e
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Thu Feb 15 20:58:16 2018 +0000

    Use libc_hidden_* for fputs (bug 15105).
    
    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 499b315324519f8deb5b42a143a76319934a3ab0)

Diff:
---
 include/stdio.h | 4 ++++
 libio/iofputs.c | 1 +
 2 files changed, 5 insertions(+)

diff --git a/include/stdio.h b/include/stdio.h
index 602434509f..820ba5491f 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -135,6 +135,10 @@ 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 b4fbeb5e60..176e9ed281 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)