Commit 8bab1c8

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cmd/cgo: don't generate random numbers for symbols

If cgo is built with -flto the symbols in runtime/cgo is going to include random numbers which would make builds unreproducible. Settings -frandom-seeds ensures this is consistent across builds, and to ensure we always use a reproducible seed across builds we use the actionID as the seed string. runtime/cgo built with "-frandom-seed=OFEc9OKoUMJwh3-5yFCH" would output the following: $ strings --all --bytes=8 $WORK/b055/_pkg_.a | grep "gnu.lto_.profile" .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797 .gnu.lto_.profile.8403a797

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src/cmd/go/internal/work
- exec.go

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`‎src/cmd/go/internal/work/exec.go`

Lines changed: 7 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -36,6 +36,7 @@ import (`
`36`	`36`	`"cmd/go/internal/modload"`
`37`	`37`	`"cmd/go/internal/str"`
`38`	`38`	`"cmd/go/internal/trace"`
	`39`	`+ "cmd/internal/buildid"`
`39`	`40`	`"cmd/internal/quoted"`
`40`	`41`	`"cmd/internal/sys"`
`41`	`42`	`)`
`@@ -2368,6 +2369,12 @@ func (b Builder) ccompile(a Action, p *load.Package, outfile string, flags []s`
`2368`	`2369`	`}`
`2369`	`2370`	`}`
`2370`	`2371`
	`2372`	`+ // Tell gcc to not insert truly random numbers into the build process`
	`2373`	`+ // this ensures LTO won't create random symbols.`
	`2374`	`+ if b.gccSupportsFlag(compiler, "-frandom-seed=1") {`
	`2375`	`+ flags = append(flags, "-frandom-seed="+buildid.HashToString(a.actionID))`
	`2376`	`+ }`
	`2377`	`+`
`2371`	`2378`	`overlayPath := file`
`2372`	`2379`	`if p, ok := a.nonGoOverlay[overlayPath]; ok {`
`2373`	`2380`	`overlayPath = p`

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Commit 8bab1c8

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1 file changed

1 file changed

`‎src/cmd/go/internal/work/exec.go`

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