This is a slightly revised version of the WIP patch against GCC 5.1 I
previously posted here:
https://gcc.gnu.org/ml/gcc/2016-05/msg00135.html
To recap, I needed a biarch x86_64 mingw-w64 target compiler that uses
DWARF-2 exception handling in 32-bit mode (for compatibility with an
older i686-mingw32 toolchain configured with --disable-sjlj-exceptions).
But, the configuration machinery was rejecting this. It used to be
that SJLJ exceptions were the only choice for 64-bit mode so it was
correct to reject --disable-sjlj-exceptions in a biarch toolchain, but
now the default for 64-bit mode is SEH instead. With this patch,
configuring with --disable-sjlj-exceptions selects DWARF-2 EH in 32-bit
mode and SEH in 64-bit mode.
I tested this in a cross-compiler configured to build C and C++ only for
x86_64 mingw-w64 target, and test results look about the same as the
default configuration, which uses SJLJ for 32-bit mode. (If it's
relevant, I also used the compiler built with the 5.1 version of the
patch to build complete Windows-host toolchains for nios2-elf and
nios2-linux-gnu, which I tested by running the GDB testsuite.) There
are no actual code changes here so I'd expect the 32-bit DWARF-2 EH
support to work exactly the same as in a 32-bit-only x86 configuration.
OK to commit?