[llvm-dev] Error Calling eraseFromParent()

[mayuyu.io via llvm-dev]

Hi:
As stated in the documentation you shouldn’t modify it while iterating as this invalidates the iterator. Try save the pointers to a vector outside your loop and perform erasing in a new loop following your current one.

Zhang

> 在 2018年8月8日，07:54，Ahmad Nouralizadeh via llvm-dev <llvm-dev at lists.llvm.org> 写道：
> 
> Thanks Bjorn! But The problem is still there.
> 
>> On Wed, Aug 8, 2018 at 2:04 AM, Björn Pettersson A <bjorn.a.pettersson at ericsson.com> wrote:
>> It looks quite dangerous to erase the instruction I inside the loop when iterating over all instructions in the function.
>> I guess it depends on how the range based iterator is implemented if that works or not.
>> 
>> I think that you, for example, can change the range based iteration
>> 
>>    for (auto &I : instructions(F))
>> 
>> into something like this
>> 
>>    for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) {
>>       Instruction *I = &*(It++);
>>       ...
>>     }
>> 
>> That will make sure that you step the iterator before modifying the data structure you iterate over.
>> 
>> Regards,
>> Björn
>> ________________________________________
>> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Ahmad Nouralizadeh via llvm-dev <llvm-dev at lists.llvm.org>
>> Sent: Tuesday, August 7, 2018 22:26
>> To: paul.robinson at sony.com
>> Cc: llvm-dev at lists.llvm.org
>> Subject: Re: [llvm-dev] Error Calling eraseFromParent()
>> 
>> The code is really simple. But I can not the reason for the segmentation fault. I only know that the eraseFromParent() function leads to it. The whole code is:
>> ...
>> bool runOnFunction(Function &F) override {
>> 
>> for (auto &I : instructions(F)) {
>> 
>> if (auto* op = dyn_cast<BinaryOperator>(&I)) {
>> IRBuilder<> builder(op);
>> 
>> Value* lhs = op->getOperand(0);
>> Value* rhs = op->getOperand(1);
>> Value* mul = builder.CreateMul(lhs, rhs);
>> 
>> for (auto& U : op->uses()) {
>>   User* user = U.getUser();
>>   user->setOperand(U.getOperandNo(), mul);
>> }
>> 
>> I.eraseFromParent();
>>     }
>> 
>> }
>> ...
>> And I think that the code worked well with LLVM-3.6.0 that I tested one year ago. Now, I use LLVM-6.0.0.
>> Regards.
> 
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