cmd/gc: clang 3.3 complains about undefined behavior

[davecheney]

What steps will reproduce the problem?

1. Download clang 3.3 or later, http://llvm.org/releases/download.html#3.3
2. export CC=clang
3. apply CL https://golang.org/cl/10488044
4. ./make.bash

What is the expected output? What do you see instead?

Expected, clean build

Actual, quite a few warnings, some trivial, others not.
https://gist.github.com/davecheney/5847237

Please use labels and text to provide additional information.

See also the discussion here
https://groups.google.com/forum/#!topic/golang-dev/SlTKGOfHjtU

[ianlancetaylor]

Comment 1:

This issue was updated by revision 5437eef.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/12388043

[rsc]

Comment 2:

This issue was updated by revision 7d734d9.

Dave, can you please try again?
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13334049

[davecheney]

Comment 3:

Thanks rsc, it's looking much better. A few warnings remain which look mostly like
signed/unsigned issues.
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
net/http/httptest
# net/http/cookiejar
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
# net/http/cookiejar
/home/dfc/go/src/libbio/bgetc.c:86:13: runtime error: left shift of 65535 by 16 places
cannot be represented in type 'int'
net/http/httputil
# net/http/cgi
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
# net/http/cgi
/home/dfc/go/src/libbio/bgetc.c:86:13: runtime error: left shift of 65535 by 16 places
cannot be represented in type 'int'
net/http/fcgi
# net/http/httptest
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
net/http/pprof
# net/http/pprof
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
net/rpc
# net/http/httputil
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
# net/http/fcgi
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
# net/rpc
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
net/rpc/jsonrpc
# net/rpc/jsonrpc
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
# net/rpc/jsonrpc
/home/dfc/go/src/libbio/bgetc.c:86:13: runtime error: left shift of 65535 by 16 places
cannot be represented in type 'int'
# cmd/go
/home/dfc/go/src/cmd/6g/gsubr.c:543:29: runtime error: left shift of negative value -1
# cmd/go
/home/dfc/go/src/libbio/bgetc.c:86:13: runtime error: left shift of 65535 by 16 places
cannot be represented in type 'int'
# cmd/go
/home/dfc/go/src/libbio/bgetc.c:86:13: runtime error: left shift of 65535 by 16 places
cannot be represented in type 'int'
/home/dfc/go/src/cmd/6l/obj.c:349:35: runtime error: left shift of negative value
-2147483648
/home/dfc/go/src/cmd/6l/span.c:1240:7: runtime error: index 22 out of bounds for type
'uchar [22]'

[rsc]

Comment 4:

This issue was updated by revision 80a153d.

R=ken2
CC=golang-dev
https://golang.org/cl/13241050

[rsc]

Comment 5:

This issue was closed by revision 6034406.

Status changed to Fixed.

[davecheney]

Comment 6:

Sorry to report there are a few more issues
A bunch are reported in the yacc generated code which I have ignored, but these two are
quite common
pkg/time
/home/dfc/go/src/cmd/6g/ggen.c:599:60: runtime error: left shift of negative value -1
/home/dfc/go/src/libmach/6obj.c:134:20: runtime error: left shift of 3435973836 by 32
places cannot be represented in type 'vlong' (aka 'long long')
pkg/os
/home/dfc/go/src/libmach/6obj.c:134:20: runtime error: left shift of 3435973836 by 32
places cannot be represented in type 'vlong' (aka 'long long')
pkg/reflect
a.y:634:28: runtime error: left shift of 2147483648 by 32 places cannot be represented
in type 'vlong' (aka 'long long')
/home/dfc/go/src/libmach/6obj.c:134:20: runtime error: left shift of 2147483648 by 32
places cannot be represented in type 'vlong' (aka 'long long')
pkg/fmt

Status changed to Accepted.

[rsc]

Comment 7:

I'm going to move this off to after Go 1.2. The left shift thing is super pedantic and I
don't believe that it affects any real compiler.

Labels changed: added go1.3maybe, removed go1.2.

[davecheney]

Comment 8:

SGTM. Thanks.

[davecheney]

Comment 9:

This issue was updated by revision 8d5ec52.

Like Tribbles, the more you kill, the more spring up in their place.
R=rsc
CC=golang-dev
https://golang.org/cl/13324049

[rsc]

Comment 10:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 11:

Labels changed: added repo-main.