[(questionable but useful) patch] Let codegen write the filename for translation unit initializer functions

[Nico Weber]

On Fri, Apr 25, 2014 at 4:33 PM, Reid Kleckner <rnk at google.com> wrote:

> This might give some assemblers heartburn.  Does gcc sanitize the filename
> in any way?
>

gcc apparently replaces spaces, '-, '+' etc with '_', so it does some
sanitizing. ("test$2.cc" ends up being just "test.cc", so their sanitizing
isn't complete.)

Does LLVM have a helper function that replaces possibly troubling
characters with '_' characters?


> What happens if the main source file is stdin?
>

gcc produces "_GLOBAL__sub_I_" (i.e. "nothing" for stdin). (My patch
currently adds a "<stdin>", which seems suboptimal :-) ).

gcc apparently only does this in -fPIC mode too, not sure why.


>
> On Fri, Apr 25, 2014 at 4:17 PM, Nico Weber <thakis at chromium.org> wrote:
>
>>  Hi,
>>
>> gcc calls the static initialization function for file foo.cc
>> _GLOBAL__sub_i_foo.cc, while clang always uses _GLOBAL__I_a . Having the
>> filename in the symbol is useful for finding where static initializers are
>> from; we use this information in chromium on linux. (On Mac, we look at the
>> dSYM file instead.)
>>
>> The attached patch makes clang behave like gcc for initializers. (It
>> doesn't change the behavior for __D_ functions, not sure if anyone wants
>> that.)
>>
>> Opinions? Is this useful for anyone else?
>>
>> (Drawbacks: slightly longer symbols, which has a (small) binary size
>> cost, and it looks like __attribute__ ((init_priority(101))) works by
>> naming the _GLOBAL__ functions _GLOBAL__I_000101 etc, so if you call your
>> source file 000101.cc it might interfere with this patch.
>>
>> Nico
>>
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>>
>
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