http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55171
Mikael Pettersson <mikpe at it dot uu.se> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mikpe at it dot uu.se
--- Comment #5 from Mikael Pettersson <mikpe at it dot uu.se> 2012-11-11
14:30:14 UTC ---
It's caused by "[patch i386]: Set for method-functions default
calling-convention to thiscall for 32-bit msabi" in r171890:
http://gcc.gnu.org/ml/gcc-patches/2011-04/msg00066.html
http://gcc.gnu.org/ml/gcc-cvs/2011-04/msg00082.html
With x86_64-w64-mingw32-g++ -m32 -O2 there are numerous code generation
differences in r171890 for this test case (as expected with the changed calling
convention), but looking only at the virtual thunk we see:
--- pr55171.s-r171889 2012-11-11 14:51:38.000000000 +0100
+++ pr55171.s-r171890 2012-11-11 15:00:58.000000000 +0100
...
__ZTv0_n16_NK7Derived3fooEv:
- movl 8(%esp), %eax
- movl (%eax), %ecx
- addl -16(%ecx), %eax
- movl %eax, 8(%esp)
+ movl 4(%esp), %eax
+ movl (%eax), %eax
+ addl -16(%eax), %eax
+ movl %eax, 4(%esp)
jmp LTHUNK2
...
The two code sequences are clearly not equivalent (ignore the stack position of
the pointer being adjusted).
Running the test case confirms: with g++ @ r171889 it succeeds, but with g++ @
r171890 it gets a runtime failure.
