Bug#665499: clang: code using std::stack *still* crashes with SIGILL when compiled with clang++

[Robert Luberda]

# most probably breaks chromium, see  #766883
severity 665499 grave
thanks

Hi, 

Clang++ 3.5 still uses `-target-cpu pentium4', so the bug is still
easily reproducible on my quite old system:

[1]/tmp> grep flags /proc/cpuinfo
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow

[2]/tmp> cat test.cpp
#include <stack>
   
int main()
{
  std::stack<int> x;
}
[3]/tmp> clang++ -v test.cpp -o testcrash
Debian clang version 3.5.0-6 (tags/RELEASE_350/final) (based on LLVM 3.5.0)
Target: i386-pc-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.9
Found candidate GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.9.1
Found candidate GCC installation: /usr/lib/gcc/i586-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i586-linux-gnu/4.9.1
Selected GCC installation: /usr/bin/../lib/gcc/i586-linux-gnu/4.9
Candidate multilib: .;@m32
Selected multilib: .;@m32
 "/usr/lib/llvm-3.5/bin/clang" -cc1 -triple i386-pc-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name test.cpp -mrelocation-model static -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -fuse-init-array -target-cpu pentium4 -target-linker-version 2.24.90.20141014 -v -dwarf-column-info -resource-dir /usr/lib/llvm-3.5/bin/../lib/clang/3.5.0 -internal-isystem /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/c++/4.9 -internal-isystem /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/i386-linux-gnu/c++/4.9 -internal-isystem /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/i386-linux-gnu/c++/4.9 -internal-isystem /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/c++/4.9/backward -internal-isystem /usr/include/clang/3.5.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-3.5/bin/../lib/clang/3.5.0/include -internal-externc-isystem /usr/bin/../lib/gcc/i586-linux-gnu/4.9/include -internal-externc-isystem /usr/include/i386-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -fdebug-compilation-dir /tmp -ferror-limit 19 -fmessage-length 106 -mstackrealign -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/user/1000/test-ca9f53.o -x c++ test.cpp
clang -cc1 version 3.5.0 based upon LLVM 3.5.0 default target i386-pc-linux-gnu
ignoring nonexistent directory "/include"
ignoring duplicate directory "/usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/i386-linux-gnu/c++/4.9"
ignoring duplicate directory "/usr/include/clang/3.5.0/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/c++/4.9
 /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/i386-linux-gnu/c++/4.9
 /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../../include/c++/4.9/backward
 /usr/include/clang/3.5.0/include
 /usr/local/include
 /usr/bin/../lib/gcc/i586-linux-gnu/4.9/include
 /usr/include/i386-linux-gnu
 /usr/include
End of search list.
 "/usr/bin/ld" --hash-style=gnu --no-add-needed --eh-frame-hdr -m elf_i386 -dynamic-linker /lib/ld-linux.so.2 -o testcrash /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../i386-linux-gnu/crt1.o /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../i386-linux-gnu/crti.o /usr/bin/../lib/gcc/i586-linux-gnu/4.9/crtbegin.o -L/usr/bin/../lib/gcc/i586-linux-gnu/4.9 -L/usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../i386-linux-gnu -L/lib/i386-linux-gnu -L/usr/lib/i386-linux-gnu -L/usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../.. -L/usr/lib/llvm-3.5/bin/../lib -L/lib -L/usr/lib /tmp/user/1000/test-ca9f53.o -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/bin/../lib/gcc/i586-linux-gnu/4.9/crtend.o /usr/bin/../lib/gcc/i586-linux-gnu/4.9/../../../i386-linux-gnu/crtn.o
[4]/tmp> ./testcrash
Illegal instruction (core dumped) 


When -march=native is passed to clang++, the generated code does not crash.

Regards,
robert