Comment 1:

bisected it. hg says:
Changeset 18077:46fd4ef6c0de: bad
Due to skipped revisions, the first bad revision could be any of:
changeset:   18074:7e10c412efea
user:        Russ Cox <rsc@golang.org>
date:        Wed Sep 11 09:56:51 2013 -0400
summary:     cmd/cgo: don't say "gcc produced no output" if we ran clang
changeset:   18075:e176e9d59540
user:        Russ Cox <rsc@golang.org>
date:        Wed Sep 11 09:57:05 2013 -0400
summary:     cmd/go: use pattern to prune file tree walk
changeset:   18076:1b195d6fe342
user:        Mikio Hara <mikioh.mikioh@gmail.com>
date:        Wed Sep 11 10:48:53 2013 -0400
summary:     net: implement TCP connection setup with fast failover
changeset:   18077:46fd4ef6c0de
user:        Russ Cox <rsc@golang.org>
date:        Wed Sep 11 11:30:08 2013 -0400
summary:     cmd/cgo: replace C.malloc with our own wrapper
had to skip revisions due to this compile error:
cmd/cgo/gcc.go:386: undefined: fixGo
cmd/cgo/gcc.go:596: undefined: fixGo
cmd/cgo/gcc.go:607: undefined: fixGo
cmd/cgo/gcc.go:656: undefined: fixGo
cmd/cgo/gcc.go:660: undefined: fixGo
cmd/cgo/gcc.go:666: undefined: fixGo
I can confirm that revision 18073:7727c1ad5ba5 works. By revision 18077:46fd4ef6c0de it
was broken.
my bisect script for posterity:
#!/bin/bash
set -xe
export GOROOT=$HOME/go
export PATH=$GOROOT/bin:$PATH
export GOOS=linux
export GOARCH=amd64
export GOHOSTARCH=amd64
export GOOSARCH=$GOOS_$GOARCH
cd $GOROOT
hg revert --all
hg purge
hg identify
cd $GOROOT/src
./make.bash || exit 125
go version || exit 125
cd $GOROOT/src/pkg/syscall
set +e
go tool cgo -godefs types_$GOOS.go >ztypes_$GOOSARCH.go
EXIT=$?
hg revert --all
exit $EXIT

Comment 2:

it might be two different problems.
the 1: error lines are probably from mkerrors.sh and the types_linux.go
lines are from go tool cgo.
the mkerrors failure is mysterious.
the go tool cgo failure might just be a missing #include.
however, neither is explained by the range of CLs you found.

Comment 3:

I'll investigate further and report back.

Comment 4:

ran this with attached file generated by mkerrors.sh:
go tool cgo -debug-define -debug-gcc -godefs -- -m64 _const.go
diff in output between working revision 7727c1ad5ba5 and tip attached.

Attachments:

1. _const.go (43065 bytes)
2. diff.txt (260890 bytes)

Comment 5:

full output of both versions might also help

Comment 6:

full output of both versions

Attachments:

1. old.txt (362117 bytes)
2. new.txt (261413 bytes)

Comment 7:

The problem is caused by this change:
 const builtinProlog = `
+#include <sys/types.h> /* for size_t below */
sys/types.h gets included without these defines:
#define _LARGEFILE_SOURCE
#define _LARGEFILE64_SOURCE
#define _FILE_OFFSET_BITS 64
#define _GNU_SOURCE
and later again with them, but I'm guessing at that point the include guards prevent
these from having any effect.

Comment 8:

Labels changed: added go1.2maybe.

Comment 9:

Thank you for the diagnosis. I can see this causing problems in real cgo programs too.
Can you please test whether CL 14684044 helps?

Labels changed: added priority-later, removed priority-triage.

Status changed to Accepted.

Comment 10:

This issue was closed by revision 5feb155.

Status changed to Fixed.