golang/go

cmd/objdump: incorrect filename for function

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#32,068 opened on May 15, 2019

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NeedsFixcompiler/runtimehelp wanted

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Description

$ go tool objdump -s cmplx.Inf ../pkg/darwin_amd64/math/cmplx.a
TEXT math/cmplx.Inf(SB) gofile..$GOROOT/src/math/bits.go
  bits.go:27		0x2e24			90			NOPL			
  isinf.go:19		0x2e25			f20f100500000000	MOVSD_XMM 0(IP), X0	[4:8]R_PCREL:$f64.7ff0000000000000	
  isinf.go:20		0x2e2d			f20f11442408		MOVSD_XMM X0, 0x8(SP)	
  isinf.go:20		0x2e33			f20f11442410		MOVSD_XMM X0, 0x10(SP)	
  isinf.go:20		0x2e39			c3			RET

Note that cmplx.Inf is listed as being in $GOROOT/src/math/bits.go. It looks like cmd/objdump may assume that the first instruction in the function is located within the function. With inlmarks in a prologue-less function, at least, this assumption is false.

Also, why is that inlining mark there in the first place?

cc @randall77 because this is an unintended consequence of inlmarks cc @dr2chase for all things position

Contributor guide

Research direction
Investigate the logic in cmd/objdump that determines the filename for a function, particularly how inlining marks affect the source location. Trace the code path from objdump to the linker or compiler output to understand why the first instruction's position is used incorrectly.
Tech stack
go
Domain
clitooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
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Active
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Clear
Prerequisites
Go
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30