[clang] [Sema] Fix memory leak in DeductionFailureInfo (#143129) (PR #143138)

[via cfe-commits]

https://github.com/lux-QAQ created https://github.com/llvm/llvm-project/pull/143138

Move allocation of deduction failure info from the ASTContext to the heap. Implement corresponding type-safe delete calls in `DeductionFailureInfo::Destroy()` to prevent memory leaks.

>From ef02e11fa1c32713ba1c0de0145db7fe504f1d03 Mon Sep 17 00:00:00 2001
From: LUX <1098346640 at qq.com>
Date: Fri, 6 Jun 2025 21:17:29 +0800
Subject: [PATCH] [Sema] Fix memory leak in DeductionFailureInfo (#143129)

Move allocation of deduction failure info from the ASTContext to the heap. Implement corresponding type-safe delete calls in `DeductionFailureInfo::Destroy()` to prevent memory leaks.
---
 clang/lib/Sema/SemaOverload.cpp | 36 +++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 66f84fc67b52f..0e059239e65cb 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -756,8 +756,8 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
 
   case TemplateDeductionResult::DeducedMismatch:
   case TemplateDeductionResult::DeducedMismatchNested: {
-    // FIXME: Should allocate from normal heap so that we can free this later.
-    auto *Saved = new (Context) DFIDeducedMismatchArgs;
+    // Allocate from normal heap so that we can free this later.
+    auto *Saved = new  DFIDeducedMismatchArgs;
     Saved->FirstArg = Info.FirstArg;
     Saved->SecondArg = Info.SecondArg;
     Saved->TemplateArgs = Info.takeSugared();
@@ -767,8 +767,8 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
   }
 
   case TemplateDeductionResult::NonDeducedMismatch: {
-    // FIXME: Should allocate from normal heap so that we can free this later.
-    DFIArguments *Saved = new (Context) DFIArguments;
+    // Allocate from normal heap so that we can free this later.
+    DFIArguments *Saved = new  DFIArguments;
     Saved->FirstArg = Info.FirstArg;
     Saved->SecondArg = Info.SecondArg;
     Result.Data = Saved;
@@ -779,8 +779,8 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
     // FIXME: It's slightly wasteful to allocate two TemplateArguments for this.
   case TemplateDeductionResult::Inconsistent:
   case TemplateDeductionResult::Underqualified: {
-    // FIXME: Should allocate from normal heap so that we can free this later.
-    DFIParamWithArguments *Saved = new (Context) DFIParamWithArguments;
+    // Allocate from normal heap so that we can free this later.
+    DFIParamWithArguments *Saved = new  DFIParamWithArguments;
     Saved->Param = Info.Param;
     Saved->FirstArg = Info.FirstArg;
     Saved->SecondArg = Info.SecondArg;
@@ -799,7 +799,8 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
     break;
 
   case TemplateDeductionResult::ConstraintsNotSatisfied: {
-    CNSInfo *Saved = new (Context) CNSInfo;
+    // Allocate from normal heap so that we can free this later.
+    CNSInfo *Saved = new CNSInfo;
     Saved->TemplateArgs = Info.takeSugared();
     Saved->Satisfaction = Info.AssociatedConstraintsSatisfaction;
     Result.Data = Saved;
@@ -831,14 +832,21 @@ void DeductionFailureInfo::Destroy() {
   case TemplateDeductionResult::IncompletePack:
   case TemplateDeductionResult::Inconsistent:
   case TemplateDeductionResult::Underqualified:
+    delete static_cast<DFIParamWithArguments*>(Data);
+    Data = nullptr;
+    break;
   case TemplateDeductionResult::DeducedMismatch:
   case TemplateDeductionResult::DeducedMismatchNested:
+    delete static_cast<DFIDeducedMismatchArgs*>(Data);
+    Data = nullptr;
+    break;
   case TemplateDeductionResult::NonDeducedMismatch:
-    // FIXME: Destroy the data?
+    // Destroy the data
+    delete static_cast<DFIArguments*>(Data);
     Data = nullptr;
     break;
 
-  case TemplateDeductionResult::SubstitutionFailure:
+  case TemplateDeductionResult::SubstitutionFailure:{
     // FIXME: Destroy the template argument list?
     Data = nullptr;
     if (PartialDiagnosticAt *Diag = getSFINAEDiagnostic()) {
@@ -846,16 +854,18 @@ void DeductionFailureInfo::Destroy() {
       HasDiagnostic = false;
     }
     break;
-
-  case TemplateDeductionResult::ConstraintsNotSatisfied:
-    // FIXME: Destroy the template argument list?
+  }
+  case TemplateDeductionResult::ConstraintsNotSatisfied:{
+    // Destroy the data
+    CNSInfo *Ptr = static_cast<CNSInfo*>(Data);
+    delete Ptr;
     Data = nullptr;
     if (PartialDiagnosticAt *Diag = getSFINAEDiagnostic()) {
       Diag->~PartialDiagnosticAt();
       HasDiagnostic = false;
     }
     break;
-
+  }
   // Unhandled
   case TemplateDeductionResult::MiscellaneousDeductionFailure:
   case TemplateDeductionResult::AlreadyDiagnosed: