[libav-devel] [PATCH] configure: Allow manually overriding the float ABI mode

Martin Storsjö martin at martin.st
Wed Aug 12 12:25:47 CEST 2015


On Wed, 12 Aug 2015, Luca Barbato wrote:

> On 12/08/15 12:12, Martin Storsjö wrote:
>> The current automatic detection might not always succeed.
>>
>> On Xcode 7 with -fembed-bitcode, the current detection fails.
>> In this case, the detection is to try to compile and link a file
>> containing '__asm__ (".eabi_attribute 28, 1");'
>>
>> With -fembed-bitcode, the assembler does print an error, but the
>> compiler process still returns a successful error code:
>>
>> $ cat test.c
>> __asm__ (".eabi_attribute 28, 1");
>> int main(void) { return 0; }
>> $ clang -arch armv7 -c test.c -fembed-bitcode -miphoneos-version-min=6.0
>> <inline asm>:1:1: error: unknown directive
>> .eabi_attribute 28, 1
>> ^
>> $ echo $?
>> 0
>>
>> This issue was pointed out by James Howe <james.howe at hp.com>.
>> ---
>> James also suggested a patch that skips the float ABI detection
>> when --disable-vfp has been set. This also would work, but that
>> disables all the VFP instruction optimizations, which is
>> a different thing than whether float arguments are passed in
>> registers or not.
>>
>> Better ways of detecting the float ABI used by apple's clang
>> are also welcomed.
>
> checking that the command actually produced a file is an option?

It actually produces a file though, I guess it only contains the bitcode 
but not any actual code (which failed to assemble).

// Martin


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