cmd/6l: CGO program will only link with MinGW 4.8.1 on Windows

[emidoots]

I have tried the following Go versions:
* Tip
* Official Go 1.3.1 binaries.

What steps reproduce the problem?

1. Extract attached zip file (5 files, 47 lines in total) to $GOPATH/src/
2. cd $GOPATH/src/mingwbug
3. go build

What happened?

C:\Users\stephen\Desktop\godev\src\mingwbug>go build -a main.go
# command-line-arguments
mingwbug/glfw(.text): mingwbug/glfw(/76): not defined
mingwbug/glfw(.text): undefined: mingwbug/glfw(/76)

What should have happened instead?

The program should link.

Please provide any additional information below.

The program compiles, links, and runs fine when using MinGW 4.8.1.

If using MinGW 4.8.3 OR 4.9.1 (MinGW-W64 project or TDM-GCC) then the linker reports the
errors above.

This issue is a minimal example if the problem we ran into at
go-gl/glfw#91 if you want more information.

[emidoots]

Comment 1:

(attachment)

Attachments:

1. mingwbug.zip (1498 bytes)

[ianlancetaylor]

Comment 2:

Please try running "go build -x" and report the results here so that we can see just
which command failed.  Thanks.

Labels changed: added repo-main, release-go1.4maybe, os-windows.

[emidoots]

Comment 3:

The output is rather large? View it in full at http://pastebin.com/1niy3W2U
C:\Users\stephen\Desktop\godev\src\mingwbug>go build -x
...trimmed by me...
cd C:\Users\stephen\Desktop\godev\src\mingwbug
"C:\\tipgoamd64\\pkg\\tool\\windows_amd64\\6g.exe" -o
"C:\\Users\\stephen\\AppData\\Local\\Temp\\go-build954290891\\mingwbug.a" -t
rimpath "C:\\Users\\stephen\\AppData\\Local\\Temp\\go-build954290891" -p mingwbug
-complete -D _/C_/Users/stephen/Desktop/godev/sr
c/mingwbug -I "C:\\Users\\stephen\\AppData\\Local\\Temp\\go-build954290891" -I
"C:\\Users\\stephen\\Desktop\\godev\\pkg\\windows_a
md64" -pack "C:\\Users\\stephen\\Desktop\\godev\\src\\mingwbug\\main.go"
cd .
"C:\\tipgoamd64\\pkg\\tool\\windows_amd64\\6l.exe" -o
"C:\\Users\\stephen\\AppData\\Local\\Temp\\go-build954290891\\mingwbug\\_obj
\\exe\\a.out.exe" -L "C:\\Users\\stephen\\AppData\\Local\\Temp\\go-build954290891" -L
"C:\\Users\\stephen\\Desktop\\godev\\pkg\\wi
ndows_amd64" -extld=gcc
"C:\\Users\\stephen\\AppData\\Local\\Temp\\go-build954290891\\mingwbug.a"
# mingwbug
mingwbug/glfw(.text): mingwbug/glfw(/76): not defined
mingwbug/glfw(.text): undefined: mingwbug/glfw(/76)

[ianlancetaylor]

Comment 4:

Sorry, I have no idea what is going on.  This is failing when running the Go linker on
Go code, so I can't see why changing the GCC version would make any difference.  I also
don't know what the "(/76)" is doing there.  This will have to be debugged by somebody
running Windows.

[rsc]

Comment 5:

Owner changed to @rsc.

Status changed to Accepted.

[rsc]

Comment 6:

The form mingwbug/glfw(name) refers to the section name inside an object in
mingwbug/glfw. The name /76 is a PE-encoded string table reference, since they only
reserved 8 letters for the section name. 
$GOROOT/src/cmd/ld/ldpe.c needs to look for the /%d form of section name and do the
appropriate translation to the correct section name.

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

Owner changed to ---.

[alexbrainman]

Comment 7:

There are 2 problems here as far as I can see (in ldpe.c):
1) section names are not read properly - that is why we see /76 in mingwbug/glfw(/76),
/76 is a reference into "string table" where real name lives;
2) ldpe.c code assumes (in a few places) that all symbols with name starting with "."
are section names - this is broken now that new gcc starts some symbols with ".".
I am not familiar with that code enough to decide how to change it safely yet. But I
will keep looking.
Alex

[alexbrainman]

Comment 8:

I had trouble finding latest gcc. http://nuwen.net/mingw.html is what I end-up using.
Alex

[andlabs]

Comment 9:

@Alex: http://mingw-w64.sourceforge.net/ - on Windows the easiest way is to use the
mingw-builds distribution.

[gopherbot]

Comment 10 by rich.amacker:

@Alex
Here's a 32-bit version:
http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/4.9.1/
Here's a 64-bit version:
http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/4.9.1/
If you go up to the parent folder, you'll find 4.8.1, 4.8.2, etc. as well.

[frederich]

Comment 11:

I'll fix the issue.

[alexbrainman]

Comment 12:

Sure, go ahead. I also have started on this issue. One of us will succeed. :-)
Alex

[frederich]

Comment 13:

Oh sorry Alex, I've thought no one is on it. You can fix it if you want?
Jens

[alexbrainman]

Comment 14:

No, please continue with your fix. I am not certain my solution is correct. Two heads
are better then one. Whoever is ready first will discuss during review.
Alex

[frederich]

Comment 15:

ok