Bug#737529: gcc-4.8: __builtin_frame_address not working on ARM

[Thomas Preud'homme <robotux@debian.org>]

Package: gcc-4.8
Version: 4.8.2-14
Severity: normal

__builtin_frame_address does not work as documented on ARM. For a value
greater or equal to 1 it returns a non null value but the returned
pointer does not seem to match a frame. See the attached testcase. With
tcc and clang it displays "__builtin_frame_address" while with gcc it
first displays "bfa1: %s" and then segfaults if the #if is removed.

Best regards,

Thomas Preud'homme

-- System Information:
Debian Release: jessie/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: armhf (armv7l)

Kernel: Linux 2.6.38-ac2-ac100 (SMP w/2 CPU cores)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages gcc-4.8 depends on:
ii  binutils        2.24-3
ii  cpp-4.8         4.8.2-14
ii  gcc-4.8-base    4.8.2-14
ii  libc6           2.17-97
ii  libcloog-isl4   0.18.1-3
ii  libgcc-4.8-dev  4.8.2-14
ii  libgmp10        2:5.1.3+dfsg-1
ii  libisl10        0.12.1-2
ii  libmpc3         1.0.1-1
ii  libmpfr4        3.1.2-1
ii  zlib1g          1:1.2.8.dfsg-1

Versions of packages gcc-4.8 recommends:
ii  libc6-dev  2.17-97

Versions of packages gcc-4.8 suggests:
ii  binutils [binutils-gold]  2.24-3
pn  gcc-4.8-doc               <none>
pn  gcc-4.8-locales           <none>
pn  libasan0-dbg              <none>
pn  libatomic1-dbg            <none>
pn  libbacktrace1-dbg         <none>
pn  libgcc1-dbg               <none>
pn  libgomp1-dbg              <none>
pn  libitm1-dbg               <none>
pn  libquadmath-dbg           <none>
pn  libtsan0-dbg              <none>

-- no debconf information

#include <stdio.h>
#include <stddef.h>

void bfa3(ptrdiff_t str_offset)
{
    printf("bfa3: %s\n", (char *)__builtin_frame_address(3) + str_offset);
}
void bfa2(ptrdiff_t str_offset)
{
    printf("bfa2: %s\n", (char *)__builtin_frame_address(2) + str_offset);
    bfa3(str_offset);
}
void bfa1(ptrdiff_t str_offset)
{
    printf("bfa1: %s\n", (char *)__builtin_frame_address(1) + str_offset);
#if defined(__arm__) && !defined(__GNUC__)
    bfa2(str_offset);
#endif
}

void builtin_frame_address_test(void)
{
    char str[] = "__builtin_frame_address";
    char *fp0 = __builtin_frame_address(0);

    printf("str: %s\n", str);
    bfa1(str-fp0);
}

int main(void)
{
    builtin_frame_address_test();
    return 0;
}