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Re: why gcc/objdump not recognize binary object file format

Hi Bridge,

I got two ARM EABI toolchain and want to test their compatibility. One
is 3.4.4 (GCC version), the other is 4.1.0. The result is 4.1.0 can
link the binary code built by 3.4.4, but on the contrary, 3.4.4 cannot
recognize binary file format built by 4.1.0.

This does not actually tell us which version of the binutils is being used. 3.4.4 is a GCC version number, not a binutils version number.

I took a look at the binutils source code. I found it's
bfd_check_format_matches that check the   file format. If target type
is not explicitly speicifed, bfd_target_vector list will be traversed
to check which target is matched. It seems this check was failed, so
the "File format not recognized" error appeared. I found below macro
do the checking.

temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));

But I didn't find abfd->xvec->_bfd_check_format[] for ARM. I cannot
know what happened in the bfd_check_format function. Any hints?

Use a debugger to follow the execution path through this pointer.

For most ELF targets you will probably end up in bfd/elfcode.h:elf_object_p(). I suspect that you will find that the checks of the machine code values are the problem. Otherwise look at the function bfd/elf32-arm.c:elf32_arm_object_p() and see if that is unable to recognise the 4.1.0 generated files.


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