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cmd/cgo: consider supporting simple variable substitution in #cgo lines #7891

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ianlancetaylor opened this issue Apr 28, 2014 · 6 comments
Closed

cmd/cgo: consider supporting simple variable substitution in #cgo lines #7891

ianlancetaylor opened this issue Apr 28, 2014 · 6 comments
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Go1.5

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@ianlancetaylor
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A common complaint about #cgo lines is that there is no way to refer to a C library
relative to the source directory.  A relative path is taken relative to the build
directory, typically in /tmp.

We should consider supporting constructs like $ORIGIN (name taken from the ELF dynamic
linker, could also be SRCDIR) which expands to the path name of the source directory.

#cgo LDFLAGS -l $ORIGIN/../lib

I don't think we should support environment variables in general.  Just a few specific
strings.  Other obvious strings would $GOARCH and $GOOS.
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Comment 1 by manoj.dayaram@moovweb.com:

That would certainly help with this issue!
https://golang.org/issue/5428

@cookieo9
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cookieo9 commented Jul 2, 2014

Comment 3:

I don't see the problem happening at tip.
On OSX 10.9 I have successfully linked a program with local libraries in a lib directory
and the cgo directive:
// #cgo LDFLAGS: -Llib -lsomelibrary
The output of go build -x --ldflags -v shows that the files in the build directory are
referenced by absolute path, and the source directory appears to be the working
directory, so relative paths seem to work.

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Comment 4 by manoj.dayaram@moovweb.com:

The issue only arises if you're running the build command outside of the directory using
the library and if the path in the #cgo line is a relative path but *not* the same
directory as the code using it.
I made fairly detailed instructions on replicating this process on this issue:
https://golang.org/issue/5428

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Comment 5:

CL https://golang.org/cl/114640044 mentions this issue.

@rsc
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rsc commented Sep 15, 2014

Comment 6:

It's too late for 1.4.

Labels changed: added release-go1.5, removed release-go1.4.

Status changed to Accepted.

@bradfitz bradfitz modified the milestone: Go1.5 Dec 16, 2014
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Gerrit CL: https://go-review.googlesource.com/#/c/1756/

@golang golang locked and limited conversation to collaborators Jun 25, 2016
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