[Mesa-dev] [PATCH v2 6/6] swr: avoid using exceptions for expected condition handling

[Cherniak, Bruce]

Reviewed-by: Bruce Cherniak <bruce.cherniak at intel.com>

> On Nov 17, 2016, at 10:56 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> 
> I was getting a weird segfault from GCC 4.9.3:
> 
> 0x00007ffff54f27aa in strlen () from /lib64/libc.so.6
> (gdb) bt
> #0  0x00007ffff54f27aa in strlen () from /lib64/libc.so.6
> #1  0x00007ffff4f128e5 in get_cie_encoding (cie=cie at entry=0x7ffff6e09813)
>     at /gcc-4.9.3/libgcc/unwind-dw2-fde.c:272
> #2  0x00007ffff4f1318e in classify_object_over_fdes (ob=ob at entry=0xd7bb90, this_fde=0x7ffff7f11010)
>     at /gcc-4.9.3/libgcc/unwind-dw2-fde.c:628
> #3  0x00007ffff4f135ba in init_object (ob=0xd7bb90)
>     at /gcc-4.9.3/libgcc/unwind-dw2-fde.c:749
> #4  search_object (ob=ob at entry=0xd7bb90, pc=pc at entry=0x7ffff4f11f4d <_Unwind_RaiseException+61>)
>     at /gcc-4.9.3/libgcc/unwind-dw2-fde.c:961
> #5  0x00007ffff4f13e62 in _Unwind_Find_registered_FDE (bases=0x7fffffffd358, pc=0x7ffff4f11f4d <_Unwind_RaiseException+61>)
>     at /gcc-4.9.3/libgcc/unwind-dw2-fde.c:1025
> #6  _Unwind_Find_FDE (pc=0x7ffff4f11f4d <_Unwind_RaiseException+61>, bases=bases at entry=0x7fffffffd358)
>     at /gcc-4.9.3/libgcc/unwind-dw2-fde-dip.c:450
> #7  0x00007ffff4f11197 in uw_frame_state_for (context=context at entry=0x7fffffffd2b0, fs=fs at entry=0x7fffffffd100)
>     at /gcc-4.9.3/libgcc/unwind-dw2.c:1245
> #8  0x00007ffff4f11b15 in uw_init_context_1 (context=context at entry=0x7fffffffd2b0, outer_cfa=outer_cfa at entry=0x7fffffffd660, outer_ra=0x7ffff518d23b <__cxa_throw+91>)
>     at /gcc-4.9.3/libgcc/unwind-dw2.c:1566
> #9  0x00007ffff4f11f4e in _Unwind_RaiseException (exc=0xd7c250)
>     at /gcc-4.9.3/libgcc/unwind.inc:88
> #10 0x00007ffff518d23b in __cxa_throw () from /usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/libstdc++.so.6
> #11 0x00007ffff51ed556 in std::__throw_out_of_range(char const*) ()
>    from /usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/libstdc++.so.6
> #12 0x00007fffea778be0 in std::map<pipe_format, SWR_FORMAT, std::less<pipe_format>, std::allocator<std::pair<pipe_format const, SWR_FORMAT> > >::at (
>     this=0x7fffebeb4c40 <mesa_to_swr_format(pipe_format)::mesa2swr>,
>     __k=@0x7fffffffd73c: PIPE_FORMAT_RGTC1_UNORM)
>     at /usr/lib/gcc/x86_64-pc-linux-gnu/4.9.3/include/g++-v4/bits/stl_map.h:549
> #13 0x00007fffea776aee in mesa_to_swr_format (format=PIPE_FORMAT_RGTC1_UNORM) at swr_screen.cpp:597
> 
> We can just void this whole issue by not using exceptions in the
> first place.
> 
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> ---
> src/gallium/drivers/swr/swr_screen.cpp | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/src/gallium/drivers/swr/swr_screen.cpp b/src/gallium/drivers/swr/swr_screen.cpp
> index aede662..36afcc3 100644
> --- a/src/gallium/drivers/swr/swr_screen.cpp
> +++ b/src/gallium/drivers/swr/swr_screen.cpp
> @@ -594,12 +594,11 @@ mesa_to_swr_format(enum pipe_format format)
>       */
>    };
> 
> -   try {
> -      return mesa2swr.at(format);
> -   }
> -   catch (std::out_of_range) {
> +   auto it = mesa2swr.find(format);
> +   if (it == mesa2swr.end())
>       return (SWR_FORMAT)-1;
> -   }
> +   else
> +      return it->second;
> }
> 
> static boolean
> -- 
> 2.7.3
> 
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