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Hi John, It seems the dereferencing a NULL pointer is undefined behavior but Calling a function through a null pointer seems o.k. If so , for this place, we need comment out the check. http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#232 look at Notes from the October 2003 meeting. Yin From: John Criswell [mailto:criswell at illinois.edu] Sent: Wednesday, November 06, 2013 6:28 PM To: Yin Ma; 'llvmdev Dev' Subject: Re: [LLVMdev] Should remove calling NULL pointer or not On 11/6/13 6:36 PM, Yin Ma...

...s undefined behavior but > > Calling a function through a null pointer seems o.k. > What is the well defined behavior of calling a null function pointer? > > > If so , for this place, we need comment out the check. > > > > http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#232 > > > > look at Notes from the October 2003 meeting. > This doesn't seem to describe well-defined behavior of calling a null function pointer. It talks about the narrow case of dereferencing a null pointer but not performing an lvalue to rvalue conversion with the resu...

On 11/6/13 6:36 PM, Yin Ma wrote: > > Hi, > > For a small case, that calls NULL pointer function. LLVM explicitly > converts > > It to a store because it thinks it is not reachable like calling > undefvalue. > > In InstCombineCalls.cpp:930 > > I think it is not a right approach because calling null pointer function > > Will segfault the program.

Hi, For a small case, that calls NULL pointer function. LLVM explicitly converts It to a store because it thinks it is not reachable like calling undefvalue. In InstCombineCalls.cpp:930 I think it is not a right approach because calling null pointer function Will segfault the program. Converting to a store will make program pass Silently. This changes the behavior of a program.