[Lldb-commits] [lldb] [lldb] IRForTarget::UnfoldConstant should return an llvm::Error (PR #195322)
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Fri May 1 11:44:19 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: Alex Langford (bulbazord)
<details>
<summary>Changes</summary>
UnfoldConstant returns a boolean and logs errors to a stream. However, the prevailing pattern is to return an Error object and let the caller decide what to do with it.
Currently, these error messages are dumped out to stdout when LLDB encoutners an issue. I decided not to change that behavior with this commit to keep it simple and self-contained.
I also reformatted and simplified some code in UnfoldConstant where it was relatively easy.
---
Full diff: https://github.com/llvm/llvm-project/pull/195322.diff
2 Files Affected:
- (modified) lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp (+47-48)
- (modified) lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h (+5-8)
``````````diff
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
index e537f76c4ed89..0c9fcedd33c50 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
@@ -15,14 +15,15 @@
#include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/Operator.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
#include "llvm/IR/ValueSymbolTable.h"
+#include "llvm/Support/ErrorExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/IPO.h"
@@ -518,16 +519,20 @@ bool IRForTarget::RewriteObjCConstString(llvm::GlobalVariable *ns_str,
->getIterator());
});
- if (!UnfoldConstant(ns_str, nullptr, CFSCWB_Caller, m_entry_instruction_finder,
- m_error_stream)) {
- LLDB_LOG(log, "Couldn't replace the NSString with the result of the call");
+ if (auto err = UnfoldConstant(ns_str, nullptr, CFSCWB_Caller,
+ m_entry_instruction_finder, m_error_stream)) {
+ std::string error_msg = llvm::toString(std::move(err));
+ LLDB_LOG(log,
+ "Couldn't replace the NSString with the result of the call: {0}",
+ error_msg);
- m_error_stream.Printf("error [IRForTarget internal]: Couldn't replace an "
+ m_error_stream.Format("error [IRForTarget internal]: Couldn't replace an "
"Objective-C constant string with a dynamic "
- "string\n");
+ "string\n{0}",
+ error_msg);
return false;
- }
+ }
ns_str->eraseFromParent();
@@ -1306,12 +1311,12 @@ bool IRForTarget::RemoveGuards(BasicBlock &basic_block) {
return true;
}
-// This function does not report errors; its callers are responsible.
-bool IRForTarget::UnfoldConstant(Constant *old_constant,
- llvm::Function *llvm_function,
- FunctionValueCache &value_maker,
- FunctionValueCache &entry_instruction_finder,
- lldb_private::Stream &error_stream) {
+llvm::Error
+IRForTarget::UnfoldConstant(Constant *old_constant,
+ llvm::Function *llvm_function,
+ FunctionValueCache &value_maker,
+ FunctionValueCache &entry_instruction_finder,
+ lldb_private::Stream &error_stream) {
SmallVector<User *, 16> users;
// We do this because the use list might change, invalidating our iterator.
@@ -1319,19 +1324,17 @@ bool IRForTarget::UnfoldConstant(Constant *old_constant,
for (llvm::User *u : old_constant->users())
users.push_back(u);
- for (size_t i = 0; i < users.size(); ++i) {
- User *user = users[i];
-
+ for (User *user : users) {
if (Constant *constant = dyn_cast<Constant>(user)) {
// synthesize a new non-constant equivalent of the constant
if (ConstantExpr *constant_expr = dyn_cast<ConstantExpr>(constant)) {
switch (constant_expr->getOpcode()) {
default:
- error_stream.Printf("error [IRForTarget internal]: Unhandled "
- "constant expression type: \"%s\"",
- PrintValue(constant_expr).c_str());
- return false;
+ return llvm::createStringErrorV(
+ "unhandled constant expression type: \"{0}\".",
+ PrintValue(constant_expr));
+
case Instruction::BitCast: {
FunctionValueCache bit_cast_maker(
[&value_maker, &entry_instruction_finder, old_constant,
@@ -1350,9 +1353,10 @@ bool IRForTarget::UnfoldConstant(Constant *old_constant,
->getIterator());
});
- if (!UnfoldConstant(constant_expr, llvm_function, bit_cast_maker,
- entry_instruction_finder, error_stream))
- return false;
+ if (auto err =
+ UnfoldConstant(constant_expr, llvm_function, bit_cast_maker,
+ entry_instruction_finder, error_stream))
+ return err;
} break;
case Instruction::GetElementPtr: {
// GetElementPtrConstantExpr
@@ -1385,33 +1389,26 @@ bool IRForTarget::UnfoldConstant(Constant *old_constant,
->getIterator());
});
- if (!UnfoldConstant(constant_expr, llvm_function,
- get_element_pointer_maker,
- entry_instruction_finder, error_stream))
- return false;
+ if (auto err = UnfoldConstant(constant_expr, llvm_function,
+ get_element_pointer_maker,
+ entry_instruction_finder, error_stream))
+ return err;
} break;
}
} else {
- error_stream.Printf(
- "error [IRForTarget internal]: Unhandled constant type: \"%s\"",
- PrintValue(constant).c_str());
- return false;
+ return llvm::createStringErrorV("unhandled constant type \"{0\".",
+ PrintValue(constant));
}
+ } else if (Instruction *inst = llvm::dyn_cast<Instruction>(user)) {
+ if (llvm_function && inst->getParent()->getParent() != llvm_function)
+ return llvm::createStringError(
+ "capturing non-local variables in expressions is unsupported.");
+
+ inst->replaceUsesOfWith(
+ old_constant, value_maker.GetValue(inst->getParent()->getParent()));
} else {
- if (Instruction *inst = llvm::dyn_cast<Instruction>(user)) {
- if (llvm_function && inst->getParent()->getParent() != llvm_function) {
- error_stream.PutCString("error: Capturing non-local variables in "
- "expressions is unsupported.\n");
- return false;
- }
- inst->replaceUsesOfWith(
- old_constant, value_maker.GetValue(inst->getParent()->getParent()));
- } else {
- error_stream.Printf(
- "error [IRForTarget internal]: Unhandled non-constant type: \"%s\"",
- PrintValue(user).c_str());
- return false;
- }
+ return llvm::createStringErrorV("unhandled non-constant type: \"{0}\".",
+ PrintValue(user));
}
}
@@ -1419,7 +1416,7 @@ bool IRForTarget::UnfoldConstant(Constant *old_constant,
old_constant->destroyConstant();
}
- return true;
+ return llvm::Error::success();
}
bool IRForTarget::ReplaceVariables(Function &llvm_function) {
@@ -1578,8 +1575,10 @@ bool IRForTarget::ReplaceVariables(Function &llvm_function) {
});
if (Constant *constant = dyn_cast<Constant>(value)) {
- if (!UnfoldConstant(constant, &llvm_function, body_result_maker,
- m_entry_instruction_finder, m_error_stream)) {
+ if (auto err =
+ UnfoldConstant(constant, &llvm_function, body_result_maker,
+ m_entry_instruction_finder, m_error_stream)) {
+ m_error_stream.Format("{0}", llvm::toString(std::move(err)));
return false;
}
} else if (Instruction *instruction = dyn_cast<Instruction>(value)) {
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h
index d710bdc950935..575d9f83b8c90 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h
@@ -382,14 +382,11 @@ class IRForTarget {
/// expression and places them before FirstEntryInstruction. These
/// instructions replace the constant uses, so UnfoldConstant calls itself
/// recursively for those.
- ///
- /// \return
- /// True on success; false otherwise
- static bool UnfoldConstant(llvm::Constant *old_constant,
- llvm::Function *llvm_function,
- FunctionValueCache &value_maker,
- FunctionValueCache &entry_instruction_finder,
- lldb_private::Stream &error_stream);
+ static llvm::Error
+ UnfoldConstant(llvm::Constant *old_constant, llvm::Function *llvm_function,
+ FunctionValueCache &value_maker,
+ FunctionValueCache &entry_instruction_finder,
+ lldb_private::Stream &error_stream);
};
#endif // LLDB_SOURCE_PLUGINS_EXPRESSIONPARSER_CLANG_IRFORTARGET_H
``````````
</details>
https://github.com/llvm/llvm-project/pull/195322
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