Fix compiler error in Attributes.cpp

[kzhuravl]

Summary

Compiling Attributes.cpp ...
../../../Attributes.cpp: In member function 'std::__1::pair<unsigned int, llvm::Optional<unsigned int> > llvm::AttributeSet::getAllocSizeArgs() const':
../../../Attributes.cpp:542:69: error: operands to ?: have different types 'std::__1::pair<unsigned int, llvm::Optional<unsigned int> >' and 'std::__1::pair<int, int>'
   return SetNode ? SetNode->getAllocSizeArgs() : std::make_pair(0, 0);
                                                                     ^
../../../Attributes.cpp:543:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^

[arsenm]

lib/IR/Attributes.cpp

542 ↗

(On Diff #94984)

Could you just add u suffixes to the 0s instead?

[kzhuravl]

lib/IR/Attributes.cpp

542 ↗

(On Diff #94984)

I could make it std::make_pair(0U, Optional<unsigned>(0)). If that is preferred?

[rnk]

Which platform exhibits this error? Also, it's an error, not a warning. The -Wreturn-type warning is a follow-on warning caused by the error in the return statement. Is this a problem with current or past versions libc++?

FWIW, I lifted this make_pair usage from elsewhere, hoping it would be portable:

std::pair<unsigned, Optional<unsigned>>
AttributeSetNode::getAllocSizeArgs() const {
  // ...
  return std::make_pair(0, 0);
}

[rnk]

lib/IR/Attributes.cpp

542 ↗

(On Diff #94984)

That or std::pair<unsigned, Optional<unsigned>>(0, 0). We don't need make_pair if it can't deduce the types.

[kzhuravl]

Address review feedback.

[kzhuravl]

In D31981#725043, @rnk wrote:

Which platform exhibits this error? Also, it's an error, not a warning. The -Wreturn-type warning is a follow-on warning caused by the error in the return statement. Is this a problem with current or past versions libc++?

FWIW, I lifted this make_pair usage from elsewhere, hoping it would be portable:

std::pair<unsigned, Optional<unsigned>>
AttributeSetNode::getAllocSizeArgs() const {
  // ...
  return std::make_pair(0, 0);
}

Thanks. g++-4.8.2 with libcxx@r264579 on Ubuntu 14.04 or 16.04.

[rnk]

lgtm

llvm/trunk/lib/IR/Attributes.cpp

uint64_t AttributeSet::getDereferenceableBytes() const {
   return SetNode ? SetNode->getDereferenceableBytes() : 0;
 }
 
 uint64_t AttributeSet::getDereferenceableOrNullBytes() const {
   return SetNode ? SetNode->getDereferenceableOrNullBytes() : 0;
 }
 
 std::pair<unsigned, Optional<unsigned>> AttributeSet::getAllocSizeArgs() const {
-  return SetNode ? SetNode->getAllocSizeArgs() : std::make_pair(0, 0);
+  return SetNode ? SetNode->getAllocSizeArgs()
+                 : std::pair<unsigned, Optional<unsigned>>(0, 0);
 }
 
 std::string AttributeSet::getAsString(bool InAttrGrp) const {
   return SetNode ? SetNode->getAsString(InAttrGrp) : "";
 }
 
 AttributeSet::iterator AttributeSet::begin() const {
   return SetNode ? SetNode->begin() : nullptr;