[LLVMdev] Possible bug in the dragonegg

[Pablo Barrio]

Hi all,

I came across something that seems to be a bug in the dragonegg option 
that emits LLVM IR. ¿Can anybody reproduce the error, or see what's 
wrong? ¿Should I post it somewhere else in case it's really a bug? 
Thanks ahead!

With this simple program:
*
#include <stdio.h>
#include <string.h>

int main(int argc, char** argv){

     char a[8] = "aaaaaaa";
     char b[8] = "bbbbbbb";

     char *c = (char*) malloc(sizeof(char)*(strlen(a)+strlen(b)+1));
     memcpy(c, a, strlen(a));
     memcpy(c + strlen(a), b, strlen(b) + 1);

     printf("a = %s, b = %s, c = %s\n", a, b, c);
}
*
and compiling and executing in the following way:

$> gcc -fplugin=~/dragonegg.so -O1 
-fplugin-arg-dragonegg-enable-gcc-optzns test.c -S 
-fplugin-arg-dragonegg-emit-ir -o test.ll

$> lli test.ll

it segfaults. If I compile without "-S -fplugin-arg-dragonegg-emit-ir", 
everything's fine. Also, if I add "-force-interpreter=true" as an lli 
parameter, I get a "LLVM ERROR: Tried to execute an unknown external 
function: memcpy". Amazingly, if I change the string sizes below 8 (e.g. 
char a[7], char b[7]), everything works just fine!! It also works if I 
move a and b outside the function (as a global), or if I malloc the 
arrays. Possibly a problem of allocation of local vars in the stack?

I also tried to link and create an assembler file so the interpreter 
could resolve the memcpy call, but neither of them work with lli:

$> llvm-link -S test.ll > test.ir

$> llvm-as test.ir -o test.s

-- 
Pablo Barrio
Dpt. Electrical Engineering - Technical University of Madrid
Office C-203
Avda. Complutense s/n, 28040 Madrid
Tel. (+34) 915495700 ext. 4234
@: pbarrio at die.upm.es

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