[LLVMdev] How to detect all free() calls

[Xi Wang]

if you don't include stdlib.h, where free() is declared, you'll simply
get a default C function signature:

int free(...);

On Mon, Mar 11, 2013 at 1:56 AM, Jane <270611649 at qq.com> wrote:
> Thanks. isFreeCall() works well but for
> %call2 = call i32 bitcast (i32 (...)* @free to i32 (i8*)*)(i8* %call1)
> nounwind, !dbg !16
> So I tried to figure out when the above instruction occurred.
> When <stdlib.h> is included,   free(buf2R1); turn into  call void @free(i8*
> %call1) nounwind, !dbg !16
> when I forget to include <stdlib.h>, free(buf2R1); turn into  %call2 = call
> i32 bitcast (i32 (...)* @free to i32 (i8*)*)(i8* %call1) nounwind, !dbg !16
> I don't understand why this is happen. Could you explain it for me?
>
> ------------------ Original ------------------
> From:  "Xi Wang"<xi.wang at gmail.com>;
> Date:  Mon, Mar 11, 2013 12:24 PM
> To:  "Jane"<270611649 at qq.com>;
> Cc:  "llvmdev"<llvmdev at cs.uiuc.edu>;
> Subject:  Re: [LLVMdev] How to detect all free() calls
>
> Try isFreeCall() defined in "llvm/Analysis/MemoryBuiltins.h".
>
> On Mon, Mar 11, 2013 at 12:17 AM, Jane <270611649 at qq.com> wrote:
>>
>> Hi,
>>     I'm trying to write a pass to detect all free()/delete() call
>> instructions in LLVM IR.The method is as follows.
>>     First I find Call Instructions: CallInst *CI=dyn_cast<CallInst>(&*i);
>>     then see if the Function name matches:
>>                         name=CI->getCalledFunction()->getName();
>> if(name=="_ZdlPv"||name=="_ZdaPv"||name=="free")
>>     It worked but when  something like this occurs
>>     %call2 = call i32 bitcast (i32 (...)* @free to i32 (i8*)*)(i8* %call1)
>> nounwind, !dbg !16
>>     It seems like a indirect function call and I don't know how to detect
>> free() in such situation.
>>     By the way, is there any way that is more convenient to detect all
>> free()/delete() call instructions in a module except by matching the
>> function name?
>>
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