hazohelet created this revision.
hazohelet added reviewers: tbaeder, aaron.ballman, cjdb.
Herald added a reviewer: NoQ.
Herald added a project: All.
hazohelet requested review of this revision.
Herald added a project: clang.
This patch checks whether `-Wunreachable-code-fallthrough` is enabled when
clang encounters unreachable fallthrough attributes and, if so, suppresses
`code will never be executed` warning to avoid duplicate warnings.
This fixes https://github.com/llvm/llvm-project/issues/60416
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D145842
Files:
clang/include/clang/Analysis/Analyses/ReachableCode.h
clang/lib/Analysis/ReachableCode.cpp
clang/lib/Sema/AnalysisBasedWarnings.cpp
clang/test/Sema/warn-unreachable-fallthrough.c
Index: clang/test/Sema/warn-unreachable-fallthrough.c
===================================================================
--- /dev/null
+++ clang/test/Sema/warn-unreachable-fallthrough.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c2x -Wunreachable-code-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c2x -Wunreachable-code %s
+// RUN: %clang_cc1 -fsyntax-only -verify=code -std=c2x -Wunreachable-code -Wno-unreachable-code-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c2x -Wno-unreachable-code -Wunreachable-code-fallthrough %s
+
+int n;
+void f(void){
+ switch (n){
+ [[fallthrough]]; // expected-warning{{fallthrough annotation in unreachable code}}
+ // code-warning@-1{{never be executed}}
+ case 1:;
+ }
+}
Index: clang/lib/Sema/AnalysisBasedWarnings.cpp
===================================================================
--- clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -123,7 +123,8 @@
return;
UnreachableCodeHandler UC(S);
- reachable_code::FindUnreachableCode(AC, S.getPreprocessor(), UC);
+ reachable_code::FindUnreachableCode(AC, S.getPreprocessor(),
+ S.getDiagnostics(), UC);
}
namespace {
Index: clang/lib/Analysis/ReachableCode.cpp
===================================================================
--- clang/lib/Analysis/ReachableCode.cpp
+++ clang/lib/Analysis/ReachableCode.cpp
@@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/ReachableCode.h"
+#include "clang/AST/Attr.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
@@ -22,6 +23,7 @@
#include "clang/Basic/Builtins.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/Preprocessor.h"
+#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallVector.h"
#include <optional>
@@ -408,15 +410,15 @@
PP(PP), C(C) {}
void enqueue(const CFGBlock *block);
- unsigned scanBackwards(const CFGBlock *Start,
- clang::reachable_code::Callback &CB);
+ unsigned scanBackwards(const CFGBlock *Start, const DiagnosticsEngine &Diag,
+ clang::reachable_code::Callback &CB);
bool isDeadCodeRoot(const CFGBlock *Block);
const Stmt *findDeadCode(const CFGBlock *Block);
- void reportDeadCode(const CFGBlock *B,
- const Stmt *S,
+ void reportDeadCode(const CFGBlock *B, const Stmt *S,
+ const DiagnosticsEngine &Diag,
clang::reachable_code::Callback &CB);
};
}
@@ -488,6 +490,7 @@
}
unsigned DeadCodeScan::scanBackwards(const clang::CFGBlock *Start,
+ const DiagnosticsEngine &Diag,
clang::reachable_code::Callback &CB) {
unsigned count = 0;
@@ -521,7 +524,7 @@
}
if (isDeadCodeRoot(Block)) {
- reportDeadCode(Block, S, CB);
+ reportDeadCode(Block, S, Diag, CB);
count += scanMaybeReachableFromBlock(Block, PP, Reachable);
}
else {
@@ -540,7 +543,7 @@
const CFGBlock *Block = I.first;
if (Reachable[Block->getBlockID()])
continue;
- reportDeadCode(Block, I.second, CB);
+ reportDeadCode(Block, I.second, Diag, CB);
count += scanMaybeReachableFromBlock(Block, PP, Reachable);
}
}
@@ -613,8 +616,8 @@
return S->getBeginLoc();
}
-void DeadCodeScan::reportDeadCode(const CFGBlock *B,
- const Stmt *S,
+void DeadCodeScan::reportDeadCode(const CFGBlock *B, const Stmt *S,
+ const DiagnosticsEngine &Diag,
clang::reachable_code::Callback &CB) {
// Classify the unreachable code found, or suppress it in some cases.
reachable_code::UnreachableKind UK = reachable_code::UK_Other;
@@ -663,6 +666,16 @@
}
}
+ // If S is `[[fallthrough]];` and `-Wunreachable-code-fallthrough` is enabled,
+ // suppress `code will never be executed` warning to avoid generating
+ // diagnostic twice
+ const AttributedStmt *AS = dyn_cast<AttributedStmt>(S);
+ if (AS && hasSpecificAttr<FallThroughAttr>(AS->getAttrs()) &&
+ !Diag.isIgnored(diag::warn_unreachable_fallthrough_attr,
+ SourceLocation())) {
+ return;
+ }
+
SourceRange R1, R2;
SourceLocation Loc = GetUnreachableLoc(S, R1, R2);
CB.HandleUnreachable(UK, Loc, SilenceableCondVal, R1, R2);
@@ -682,7 +695,7 @@
}
void FindUnreachableCode(AnalysisDeclContext &AC, Preprocessor &PP,
- Callback &CB) {
+ const DiagnosticsEngine &Diag, Callback &CB) {
CFG *cfg = AC.getCFG();
if (!cfg)
@@ -713,11 +726,10 @@
continue;
DeadCodeScan DS(reachable, PP, AC.getASTContext());
- numReachable += DS.scanBackwards(block, CB);
+ numReachable += DS.scanBackwards(block, Diag, CB);
if (numReachable == cfg->getNumBlockIDs())
return;
}
}
-
}} // end namespace clang::reachable_code
Index: clang/include/clang/Analysis/Analyses/ReachableCode.h
===================================================================
--- clang/include/clang/Analysis/Analyses/ReachableCode.h
+++ clang/include/clang/Analysis/Analyses/ReachableCode.h
@@ -13,6 +13,7 @@
#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_REACHABLECODE_H
#define LLVM_CLANG_ANALYSIS_ANALYSES_REACHABLECODE_H
+#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/SourceLocation.h"
//===----------------------------------------------------------------------===//
@@ -61,8 +62,7 @@
llvm::BitVector &Reachable);
void FindUnreachableCode(AnalysisDeclContext &AC, Preprocessor &PP,
- Callback &CB);
-
+ const DiagnosticsEngine &Diag, Callback &CB);
}} // end namespace clang::reachable_code
#endif
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