Re: [Gcc4cli-devel] Mono.Cecil: Fixing wrong prototypes at link time

[David Y. <dav...@in...>]

Hi,

  I updated the link time mechanism for fixing prototypes. Now it works without problems and it detects bugs such as calls with incorrect number of arguments in the source code.
  Thanks to it I was able to identify several actual bugs in benchmarks such as SPEC2000:176.gcc, and properly fix them.

  Soon I will update the actual driver implementation. Any way, we must merge with the new Cecil.

David

----- Mail original -----
> De: "David Yuste" <dav...@in...>
> À: gcc...@li...
> Envoyé: Vendredi 6 Mai 2011 18:26:32
> Objet: [Gcc4cli-devel] Mono.Cecil: Fixing wrong prototypes at link time
> Hi,
> 
> I developed a small method to fix prototypes at link time (thus, it is
> implemented in Mono.Cecil).
> 
> Basically, it compares the signature of each function involved in a
> *direct* call with the signature of the corresponding function
> definition. If they differ (right now I only care about the return
> value), it updates the signature in the call statement. In addition,
> if the call signature was "not void" typed, while the actual function
> is "void" typed, the next instruction is checked. If this instruction
> is "pop", it is deleted (thus we avoid an incorrect stack error).
> 
> As limitation, it doesn't apply to indirect calls (since we don't know
> the callee function).
> 
> Since I don't have write access to the Mono.Cecil repository (and also
> we work on a version, why?), I just attach the patch. I'm still
> experiencing with it, but it worked properly in all my tests.
> 
> Finally, just an example of the problem and the solution (introduced
> at link time):
> 
> *** Source code
> file1.c
> ---
> void foo (char ** argv) {
> }
> ---
> 
> file2.c
> ---
> int main (int argc, char ** argv) {
> foo (argv); -> guessed as 'int foo (char**)'
> }
> ---
> 
> *** After cil32
> file1.cil32
> ---
> .method public static void 'foo' (int8 * * 'argv') cil managed
> {
> ...
> }
> ---
> 
> file2.cil32
> ---
> .method public static int32 'main' (int32 'argc', int8 * * 'argv') cil
> managed {
> ...
> call int32 [ExternalAssembly]ExternalAssembly::'no_prototype' (native
> int)
> pop
> ldc.i4 0
> ...
> }
> ---
> 
> *** After link (with our pass)
> .method public static
> default int32 main (int32 argc, int8** argv)
> cil managed
> {
> // Method begins at RVA 0x2084
> // Code size 9 (0x9)
> .maxstack 8
> IL_0000: ldarg.1
> IL_0001: conv.i
> IL_0002: call void test::foo(int8**) //Fixed return value
> IL_0007: ldc.i4.0 //Pop removed, the stack is correct
> IL_0008: ret
> } // end of method test::main
> 
> 
> David
> 
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