[Bug tree-optimization/69522] New: gcc hangs on valid code on x86_64-linux-gnu

[helloqirun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69522

            Bug ID: 69522
           Summary: gcc hangs on valid code on x86_64-linux-gnu
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: helloqirun at gmail dot com
  Target Milestone: ---

The current gcc trunk hangs on the following valid code snippets on
x86_64-linux-gnu in both 32-bit and 64-bit modes.

I assume the code snippets are valid since both gcc-4.4 and clang-trunk compile
them. gcc-4.4 and clang-trunk generate no warning for the first code snippet.
The second one is essentially the same as the first one having the line control
removed.

I tested them for gcc-4.6, gcc-4.8, gcc-4.9, gcc-5.1, gcc-5.2 and gcc-5.3. Only
gcc-4.8 got an ICE for "abc2.c", the others were just hanging.


$ gcc-4.4 -Wall -Wextra abc1.c -c
$ clang-trunk -Wall -Wextra -Wpedantic abc1.c -c
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/home/absozero/trunk/root-gcc/libexec/gcc/x86_64-pc-linux-gnu/6.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --prefix=/home/absozero/trunk/root-gcc
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 6.0.0 20160127 (experimental) [trunk revision 232874] (GCC) 


$ time gcc-trunk abc1.c
^C

real    21m50.378s
user    0m0.000s
sys     0m0.002s



$ cat abc1.c
# 1 "" 3
struct str {};
struct {
  struct str b;
  float c[4];
  int d;
  float e[2];
  int f;
} a = {{}, 0, 0, 0, 0, {0.5}, 0, 0, {0}};


================


$ time gcc-trunk abc2.c
abc.c:8:1: warning: braces around scalar initializer
 } a = {{}, 0, 0, 0, 0, {0.5}, 0, 0, {0}};
 ^
abc.c:8:1: note: (near initialization for ‘a.d’)
abc.c:8:1: warning: braces around scalar initializer
abc.c:8:1: note: (near initialization for ‘a.f’)
^C

real    14m22.631s
user    0m0.000s
sys     0m0.002s


$ gcc-4.8 abc2.c
abc.c:8:1: warning: braces around scalar initializer [enabled by default]
 } a = {{}, 0, 0, 0, 0, {0.5}, 0, 0, {0}};
 ^
abc.c:8:1: warning: (near initialization for ‘a.d’) [enabled by default]
abc.c:8:1: internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-4.8/README.Bugs> for instructions.
Preprocessed source stored into /tmp/ccVkQrfE.out file, please attach this to
your bugreport.


$cat abc2.c
struct str {};
struct {
  struct str b;
  float c[4];
  int d;
  float e[2];
  int f;
} a = {{}, 0, 0, 0, 0, {0.5}, 0, 0, {0}};