[LLVMdev] Another memory fun

[Brendan Younger]

On Jan 6, 2008, at 12:29 PM, Zalunin Pavel wrote:

> Hey again)
>
> Now I have next code:
>
> ; ModuleID = 'sample.lz'
> @.str1 = internal global [8 x i8] c" world!\00"         ; <[8 x  
> i8]*> [#uses=1]
> @.str2 = internal global [8 x i8] c"hello, \00"         ; <[8 x  
> i8]*> [#uses=1]
> @.str7 = internal global [21 x i8] c"welcome to out hall! 
> \00"           ; <[21 x i8]*> [#uses=1]
>
> declare i32 @puts(i8*)
>
> declare i8* @strcat(i8*, i8*)
>
> declare void @llvm.memcpy.i32(i8*, i8*, i32, i32)
>
> define i32 @main() {
> mainBlock:
>         %.str3 = getelementptr [8 x i8]* @.str2, i64 0, i64  
> 0           ; <i8*> [#uses=1]
>         %.str4 = getelementptr [8 x i8]* @.str1, i64 0, i64  
> 0           ; <i8*> [#uses=1]
>         %tmp5 = call i8* @strcat( i8* %.str3, i8*  
> %.str4 )              ; <i8*> [#uses=1]
>         %tmp6 = call i32 @puts( i8* %tmp5 )             ; <i32>  
> [#uses=0]
>         %.str8 = getelementptr [21 x i8]* @.str7, i64 0, i64  
> 0          ; <i8*> [#uses=1]
>         %tmp9 = call i32 @puts( i8* %.str8 )            ; <i32>  
> [#uses=0]
>         ret i32 0
> }

You should look more closely at the man page for strcat().  You have  
to have sufficient space in the buffer for the first argument.   
Otherwise you're trashing memory.

Brendan Younger