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cmd/compile: off-by-many in line number reported for compile error #8836

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dominikh opened this issue Sep 29, 2014 · 5 comments
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cmd/compile: off-by-many in line number reported for compile error #8836

dominikh opened this issue Sep 29, 2014 · 5 comments
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Go1.5

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@dominikh
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What does 'go version' print?
go version go1.3.2 linux/amd64

What steps reproduce the problem?
If possible, include a link to a program on play.golang.org.

1. Compile http://play.golang.org/p/V41ws9TExS
2.
3.

What happened?
# _/tmp/foo
./foobar.go:12: cannot use 42 (type int) as type *C.int in argument to _Cfunc_foobar


What should have happened instead?
# _/tmp/foo
./foobar.go:15: cannot use 42 (type int) as type *C.int in argument to _Cfunc_foobar

Please provide any additional information below.
The error is always reported for line 12, even if more arguments are added to the
function. If the first argument of foobar is changed from int* to int, (and the call
adjusted appropriately), the error is instead reported for line 16, which is another
off-by-one error.
@ianlancetaylor
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Comment 1:

Labels changed: added repo-main, release-go1.5.

Status changed to Accepted.

@ianlancetaylor
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Comment 2:

Actually this has nothing to do with cgo, the Go compiler has the same problem.
http://play.golang.org/p/XgU4-2ryvT

@bradfitz bradfitz modified the milestone: Go1.5 Dec 16, 2014
@rsc rsc removed accepted labels Apr 14, 2015
@rsc
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rsc commented May 19, 2015

@dr2chase another

@dr2chase
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This looks intractable and annoying -- I think the root cause is our tendency to sometimes construct ASTs that aren't trees, so that when an argument to a function call is a shared node in the AST its line number is not trustworthy. It is possible to get it right for numbers, but not for boolean constants true and false.

You can see the hackiness in setlineno around line 230 of subr.go; that uses the line number of a node to set the global lineno (a hack in itself if you ask me) but only when the node is not a ONAME, OTYPE, OPACK, or OLITERAL.

@rsc rsc changed the title cmd/gc: off-by-many in line number reported for compile error cmd/compile: off-by-many in line number reported for compile error Jun 8, 2015
@josharian josharian mentioned this issue Jun 25, 2015
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@gopherbot
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CL https://golang.org/cl/11672 mentions this issue.

@rsc rsc closed this as completed in 55203c7 Jun 29, 2015
@dominikh dominikh mentioned this issue Apr 27, 2016
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@golang golang locked and limited conversation to collaborators Jun 28, 2016
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@bradfitz @dominikh @rsc @dr2chase @ianlancetaylor @gopherbot