• Ian Lance Taylor's avatar
    cmd/go: add support for build IDs with gccgo · fc408b62
    Ian Lance Taylor authored
    This just adds support on ELF systems, which is OK for now since that
    is all that gccgo works on.
    
    For the archive file generated by the compiler we add a new file
    _buildid.o that has a section .go.buildid containing the build ID.
    Using a new file lets us set the SHF_EXCLUDE bit in the section header,
    so the linker will discard the section. It would be nicer to use
    `objcopy --add-section`, but objcopy doesn't support setting the
    SHF_EXCLUDE bit.
    
    For an executable we just use an ordinary GNU build ID. Doing this
    required modifying cmd/internal/buildid to look for a GNU build ID,
    and use it if there is no other Go-specific note.
    
    This CL fixes a minor bug in gccgoTOolchain.link: it was using .Target
    instead of .built, so it failed for a cached file.
    
    This CL fixes a bug reading note segments: the notes are aligned as
    reported by the PT_NOTE's alignment field.
    
    Updates #22472
    
    Change-Id: I4d9e9978ef060bafc5b9574d9af16d97c13f3102
    Reviewed-on: https://go-review.googlesource.com/85555
    Run-TryBot: Ian Lance Taylor <iant@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarRuss Cox <rsc@golang.org>
    fc408b62
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testdata Loading commit data...
buildid.go Loading commit data...
buildid_test.go Loading commit data...
note.go Loading commit data...
rewrite.go Loading commit data...