code review 129160043: cmd/cgo: check for compiler errors in the C preamble

cmd/cgo: check for compiler errors in the C preamble

E.g., here's the new "go build" output:

$ go build misc/cgo/errors/issue8442.go
# command-line-arguments
could not determine kind of name for C.issue8442foo

gcc errors for preamble:
misc/cgo/errors/issue8442.go:11:19: error: unknown type name 'UNDEF'

Fixes issue 8442.

[mdempsky, 2014-08-14 00:20:07]

Hello iant@golang.org (cc: golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go

[mdempsky, 2014-08-14 00:22:53]

First stab at this problem.  Couple questions in my mind:
1. Is there a good way to automatically test this?
2. Is the output messaging good?
3. In the !completed case, should we print the preamble errors too?

[iant, 2014-08-14 01:23:13]

I think it is a good idea to check for preamble errors in the !completed case.

As far as I can see you can add another test case to misc/cgo/errors for this. 
Anything that points the user at a line in their file is better than we do
today.

[brainman, 2014-08-14 05:45:57]

FYI. I rerun program from the issue. The error message changed from:

C:\go\path\mine\src\issue8442>go run a.go
# command-line-arguments
37: error: 'EnumProcesses' undeclared (first use in this function)

to:

C:\go\path\mine\src\issue8442>go run a.go
# command-line-arguments
could not determine kind of name for C.EnumProcesses

compiler output:
In file included from .\a.go:3:0:
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:30:2:
error: expected specifier-qualifier-list before 'LPVOID'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:36:2:
error: expected specifier-qualifier-list before 'LPVOID'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:41:2:
error: expected specifier-qualifier-list before 'DWORD'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:54:2:
error: expected specifier-qualifier-list before 'DWORD'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:68:3:
error: expected specifier-qualifier-list before 'DWORD'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:85:3:
error: expected specifier-qualifier-list before 'ULONG_PTR'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:96:3:
error: expected specifier-qualifier-list before 'ULONG_PTR'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:101:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:102:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:103:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:104:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:105:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:106:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:107:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:108:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:109:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:110:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:111:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:112:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:113:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:114:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:115:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:116:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:117:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:118:7:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:119:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'
c:\go\mingw\bin\../lib/gcc/mingw32/4.5.2/../../../../include/psapi.h:120:6:
error: expected '=', ',', ';', 'asm' or '__attribute__' before 'WINAPI'

Alex

[mdempsky, 2014-08-14 06:50:48]

PTAL

On 2014/08/14 01:23:13, iant wrote:
> I think it is a good idea to check for preamble errors in the !completed case.

It seems easier/better to just print the full error output as the problem there
might not be in the preamble, and I'm happy to revisit this decision if it
proves problematic.  The error output is already a bit verbose in this case, so
I don't think this makes it much worse.  See below for an example.

> As far as I can see you can add another test case to misc/cgo/errors for this.

> Anything that points the user at a line in their file is better than we do
> today.

Done.  (Duh, for some reason I thought misc/cgo/errors could only be used for
errors in the Go code, but of course because of #line output it's fine for cgo C
preamble code too.)

On 2014/08/14 05:45:57, brainman wrote:
> FYI. I rerun program from the issue. The error message changed from: [...] to:
[...]

Thanks Alex!  My non-Windows-programmer eye thinks the new error output looks
more usable.  Do you agree, or do you think there's more that cgo could do here?


$ go tool cgo -- -Wfatal-errors issue8442.go
gcc did not produce error at completed:1
on input:
#line 10 "/home/mdempsky/go/misc/cgo/errors/issue8442.go"

void issue8442foo(UNDEF*); // ERROR HERE


#include <stddef.h> /* for ptrdiff_t and size_t below */

/* Define intgo when compiling with GCC.  */
typedef ptrdiff_t intgo;

typedef struct { char *p; intgo n; } _GoString_;
typedef struct { char *p; intgo n; intgo c; } _GoBytes_;
_GoString_ GoString(char *p);
_GoString_ GoStringN(char *p, int l);
_GoBytes_ GoBytes(void *p, int n);
char *CString(_GoString_);
void *_CMalloc(size_t);
#line 1 "not-declared"
void __cgo_f_1_1(void) { __typeof__(issue8442foo) *__cgo_undefined__; }
#line 1 "not-type"
void __cgo_f_1_2(void) { issue8442foo *__cgo_undefined__; }
#line 1 "not-const"
void __cgo_f_1_3(void) { enum { __cgo__undefined__ = (issue8442foo)*1 }; }
#line 1 "completed"
int __cgo__1 = __cgo__2;

full error output:
/home/mdempsky/go/misc/cgo/errors/issue8442.go:11:19: error: unknown type name
'UNDEF'
compilation terminated due to -Wfatal-errors.

[brainman, 2014-08-14 06:59:11]

On 2014/08/14 06:50:48, mdempsky wrote:
> 
> ...  My non-Windows-programmer eye thinks the new error output looks
> more usable.  Do you agree, ...

I do. The output looks more confusing then before. :-) And that is what I would
want in this instance. Thank you.

Alex

[iant, 2014-08-14 16:17:53]

LGTM

[iant, 2014-08-14 16:22:05]

*** Submitted as https://code.google.com/p/go/source/detail?r=3b864e02b987 ***

cmd/cgo: check for compiler errors in the C preamble

E.g., here's the new "go build" output:

$ go build misc/cgo/errors/issue8442.go
# command-line-arguments
could not determine kind of name for C.issue8442foo

gcc errors for preamble:
misc/cgo/errors/issue8442.go:11:19: error: unknown type name 'UNDEF'

Fixes issue 8442.

LGTM=iant
R=iant, alex.brainman
CC=golang-codereviews
https://codereview.appspot.com/129160043

Committer: Ian Lance Taylor <iant@golang.org>

[gobot, 2014-08-15 12:25:12]

This CL appears to have broken the linux-arm-arm5 builder.
See http://build.golang.org/log/b1da630f30c600adef5b1cffe052eef3c4501da7

[dfc, 2014-08-15 12:26:44]

Sorry, I'm going to take that builder offline to figure out what has happened.

On Fri, Aug 15, 2014 at 10:25 PM,  <gobot@golang.org> wrote:
> This CL appears to have broken the linux-arm-arm5 builder.
> See http://build.golang.org/log/b1da630f30c600adef5b1cffe052eef3c4501da7
>
>
> https://codereview.appspot.com/129160043/
>
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