Bug#826555: gcc-snapshot regression: -Warray-bounds false positive with -O2

[Vincent Lefevre <vincent@vinc17.net>]

Package: gcc-snapshot
Version: 20160603-1
Severity: important
Tags: upstream
Forwarded: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71433

When compiling GNU MPFR 3.1.4 with CFLAGS="-O2 -Werror=array-bounds" and

gcc (Debian 20160603-1) 7.0.0 20160603 (experimental) [trunk revision 237077]

I get:

get_d.c: In function 'mpfr_get_d':
get_d.c:115:24: error: array subscript is above array bounds [-Werror=array-bounds]
             d = (d + tp[i]) / MP_BASE_AS_DOUBLE;
                      ~~^~~

There was no such problem with

gcc (Debian 20160508-1) 7.0.0 20160508 (experimental) [trunk revision 236009]

so that's a recent regression.

I've also reported the bug upstream.

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'stable-updates'), (500, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.5.0-2-amd64 (SMP w/12 CPU cores)
Locale: LANG=POSIX, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gcc-snapshot depends on:
ii  binutils             2.26-10
ii  libasound2           1.1.0-1
ii  libatk1.0-0          2.20.0-1
ii  libc6                2.22-10
ii  libc6-dev            2.22-10
ii  libc6-dev-i386       2.22-10
ii  libc6-dev-x32        2.22-10
ii  libc6-i386           2.22-10
ii  libc6-x32            2.22-10
ii  libcairo2            1.14.6-1+b1
ii  libecj-java          3.10.1-2
ii  libfontconfig1       2.11.0-6.4
ii  libfreetype6         2.6.3-3+b1
ii  libgdk-pixbuf2.0-0   2.34.0-1
ii  libglib2.0-0         2.48.1-1
ii  libgmp10             2:6.1.0+dfsg-2
ii  libgtk2.0-0          2.24.30-2
ii  libice6              2:1.0.9-1+b1
ii  libisl15             0.17.1-1
ii  libmpc3              1.0.3-1
ii  libmpfr4             3.1.4-2
ii  libpango-1.0-0       1.40.1-1
ii  libpangocairo-1.0-0  1.40.1-1
ii  libpangoft2-1.0-0    1.40.1-1
ii  libsm6               2:1.2.2-1+b1
ii  libxrandr2           2:1.5.0-1
ii  libxrender1          1:0.9.9-2
ii  libxtst6             2:1.2.2-1+b1
ii  python               2.7.11-2
ii  zlib1g               1:1.2.8.dfsg-2+b1

gcc-snapshot recommends no packages.

Versions of packages gcc-snapshot suggests:
ii  binutils [binutils-gold]  2.26-10

-- no debconf information