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gccgo: very long gcbits symbol names #32083

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Helflym opened this issue May 16, 2019 · 3 comments
Closed

gccgo: very long gcbits symbol names #32083

Helflym opened this issue May 16, 2019 · 3 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Gccgo

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@Helflym
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Helflym commented May 16, 2019 •
edited

gccgo is generated gcbits symbols with their full name, instead of hidding them under gcbits..* like Go toolchain is doing (cf https://go-review.googlesource.com/c/go/+/12531/).
Corresponding Go issue #11583

$ nm index0-out.o | grep gcbits  
...
gcbits..bazaaaaaaaamaaa... (average 100 000 a... )
...

On AIX, symbol names are limited to 65535 characters.
Therefore, test "./index0-out.go compilation" is failing:

ld: 0711-950 ERROR: A name is too long.
        Names longer than 65535 characters are truncated.
        The name begins: gcbits..bazaaaaaaaamaaaaaaaaaaaaaaaaaaaaaaaaa
ld: 0711-950 ERROR: A name is too long.
        Names longer than 65535 characters are truncated.
        The name begins: gcbits..bazaaaaaaaamaaaaaaaaaaaaaaaaaaaaaaaaa
collect2: error: ld returned 8 exit status
compiler exited with status 1

Is there any way to reduce/hide these symbol names as it's done under Go toolchain ?
I don't think such thing can actually occur in a "real" Go code, but that might be worth fixing it once for all.

/cc @ianlancetaylor @thanm
@gopherbot gopherbot added this to the Gccgo milestone May 16, 2019
@thanm
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thanm commented May 16, 2019

Could you please post the code in question, or some sort of source reproducer? Thanks.

@Helflym
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Helflym commented May 16, 2019

index0-out.zip

This index0-out.go is generated inside gccgo testsuite (under gcc/testsuite/go.test/test) by index0.go and index.go.

@thanm thanm self-assigned this May 16, 2019
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Change https://golang.org/cl/177598 mentions this issue: compiler: use SHA1-hash for symname for long gcbits symbols

@ALTree ALTree added the NeedsFix The path to resolution is known, but the work has not been done. label May 17, 2019
kraj pushed a commit to kraj/gcc that referenced this issue May 17, 2019
compiler: use SHA1-hash for symname for long gcbits symbols
ef1ddaf 
    
    The current scheme used by the compiler for "gcbits" symbols involves
    generating a symbol name based on a 32-char encoding of the bits data.
    This scheme works well in most cases but can generate very long symbol
    names in rare cases. To help avoid such long symbol names, switch to a
    different encoding scheme based on the SHA1 digest of the payload if
    the symbol size would be too large.
    
    Fixes golang/go#32083.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/177598


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@271322 138bc75d-0d04-0410-961f-82ee72b054a4
@golang golang locked and limited conversation to collaborators May 16, 2020
@rsc rsc unassigned thanm Jun 23, 2022
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