[cfe-dev] Clang tooling and cross compiled code bases

Andrew McGregor andrewmcgr at gmail.com
Sun Sep 9 21:15:30 PDT 2012

On 10/09/2012, at 12:43 PM, Andrew McGregor <andrewmcgr at gmail.com> wrote:

> On 7/09/2012, at 8:57 PM, Manuel Klimek <klimek at google.com> wrote:
>> On Fri, Sep 7, 2012 at 3:36 AM, Andrew McGregor <andrewmcgr at gmail.com> wrote:
>>> I have an issue where I'm trying to use a libTooling based refactoring tool on a codebase that is intended for cross-compilation.  I have hacked together means to create a compile_commands.json, but the tool is ignoring -triple and -internal-isystem and therefore getting the sizes of many basic types wrong since my compile host is 64 bit and the target isn't.
>>> Is there a straightforward way of resolving this?
>> I'd say: it's a bug :) Is there an easy way to reproduce this in a
>> small example?
> I'll try to construct one.  Don't hold your breath, this is a background job.
> Andrew

Ok, I did get time, so here we go.  Given compile_commands.json containing (obviously, change paths as appropriate):

        "command": "clang -fno-signed-char -c -o foo.o foo.c", 
        "directory": "/home/andrewm/source/hack/minimal-clang-cc-problem", 
        "file": "/home/andrewm/source/hack/minimal-clang-cc-problem/foo.c",

and foo.c in the appropriate place containing:

#include <stdio.h>
#include <stdint.h>

void oinker(char *it) {
  printf("%s\n", it);

int main(int argc, char **argv) {
  uint64_t foo;
  uint8_t oink[] = "oink";

  return 0;

$ clang-check -p=/home/andrewm/source/hack/minimal-clang-cc-problem/ /home/andrewm/source/hack/minimal-clang-cc-problem/foo.c
Processing: /home/andrewm/source/hack/minimal-clang-cc-problem/foo.c.
warning: argument unused during compilation: '-fno-signed-char'
foo.c:12:10: warning: passing 'uint8_t [5]' to parameter of type 'char *' converts between pointers to integer types with different sign [-Wpointer-sign]
foo.c:4:19: note: passing argument to parameter 'it' here
void oinker(char *it) {
1 warning generated.

I would argue that -fno-signed-char should be respected in this situation.

The same sort of thing applies to many arguments, including -triple (but not -target) and -isystem-internal.

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