llvm dev - Aug 2018 - 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.

On Tue, Aug 7, 2018 at 8:11 PM, <paul.robinson at sony.com> wrote:
> LLVMSymbolizer is invoked while trying to pretty-print a crash backtrace.
> "error reading file" suggests that you are on Windows and it
cannot find
> the .pdb file with symbol information.
>
> If that's the case, are you doing either a Debug or RelWithDebInfo
build?
> If you are, I don't know what else to suggest.
>
>
>
> Note that LLVMSymbolizer is trying to make the traceback more
> understandable; it has nothing to do with the cause of your problem.  If
> you are triggering an assertion, the assertion message should tell you
> where that is.  (You did run cmake with –DLLVM_ENABLE_ASSERTIONS=ON,
> right?)  If not, likely you are dereferencing a null pointer somewhere.
> Personally I debug with 'printf' statements, but that's just
me.
>
> --paulr
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of
*Ahmad
> Nouralizadeh via llvm-dev
> *Sent:* Tuesday, August 07, 2018 11:03 AM
> *To:* llvm-dev at lists.llvm.org
> *Subject:* [llvm-dev] Error Calling eraseFromParent()
>
>
>
> Hi.
>
> This is part of my code:
>
> ...
>
> if (auto* op = dyn_cast<BinaryOperator>(&I)) {
>
>    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();
>
> }
>
> ...
>
> This leads to the following runtime error:
>
> LLVMSymbolizer: error reading file: No such file or directory
>
> ...
>
> Does anybody know the solution?
>
> Regards.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180808/c96b2204/attachment.html>

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.

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.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20180808/9d592482/attachment.html>