[clang-tools-extra] b0cb331 - [clang-tidy] Avoid brace fix-it crash in macro body expansion (#198788)

[via cfe-commits]

Author: Zeyi Xu
Date: 2026-06-04T16:29:06+08:00
New Revision: b0cb331995d494dda75d5fd967e160ec0c32caf1

URL: https://github.com/llvm/llvm-project/commit/b0cb331995d494dda75d5fd967e160ec0c32caf1
DIFF: https://github.com/llvm/llvm-project/commit/b0cb331995d494dda75d5fd967e160ec0c32caf1.diff

LOG: [clang-tidy] Avoid brace fix-it crash in macro body expansion (#198788)

`readability-braces-around-statements `could assert when diagnosing an
unbraced statement that ends in the middle of a macro body expansion. It
would be hard/unsafe to give fix-its for such cases, so treat them as
diagnostic-only.

Closes https://github.com/llvm/llvm-project/issues/198711

Added: 
    

Modified: 
    clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
    clang-tools-extra/clang-tidy/utils/BracesAroundStatement.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements-same-line.cpp
    clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp b/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
index 1864dfcbd29c2..710b538317626 100644
--- a/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp
@@ -154,7 +154,8 @@ bool BracesAroundStatementsCheck::checkStmt(
       S, Result.Context->getLangOpts(), *Result.SourceManager, StartLoc,
       EndLocHint);
   if (BraceInsertionHints) {
-    if (ShortStatementLines && !ForceBracesStmts.erase(S) &&
+    if (ShortStatementLines && BraceInsertionHints.offersFixIts() &&
+        !ForceBracesStmts.erase(S) &&
         BraceInsertionHints.resultingCompoundLineExtent(*Result.SourceManager) <
             ShortStatementLines)
       return false;

diff  --git a/clang-tools-extra/clang-tidy/utils/BracesAroundStatement.cpp b/clang-tools-extra/clang-tidy/utils/BracesAroundStatement.cpp
index d51bfd9362eb7..151fec67228c7 100644
--- a/clang-tools-extra/clang-tidy/utils/BracesAroundStatement.cpp
+++ b/clang-tools-extra/clang-tidy/utils/BracesAroundStatement.cpp
@@ -110,7 +110,9 @@ BraceInsertionHints getBraceInsertionsHints(const Stmt *const S,
   // 2) If there's a multi-line block comment starting on the same line after
   // the location we're inserting the closing brace at, or there's a non-comment
   // token, the check inserts "\n}" right before that token.
-  // 3) Otherwise the check finds the end of line (possibly after some block or
+  // 3) If the statement ends in the middle of a macro body expansion, the check
+  // emits a diagnostic without a fix-it.
+  // 4) Otherwise the check finds the end of line (possibly after some block or
   // line comments) and inserts "\n}" right before that EOL.
   if (!S || isa<CompoundStmt>(S)) {
     // Already inside braces.
@@ -157,6 +159,12 @@ BraceInsertionHints getBraceInsertionsHints(const Stmt *const S,
     EndLoc = EndLocHint;
     ClosingInsertion = "} ";
   } else {
+    const SourceLocation StmtEndLoc = S->getEndLoc();
+    if (StmtEndLoc.isMacroID() && SM.isMacroBodyExpansion(StmtEndLoc) &&
+        !Lexer::isAtEndOfMacroExpansion(StmtEndLoc, SM, LangOpts)) {
+      // No safe fix-it for a statement ending in the middle of a macro body.
+      return {StartLoc};
+    }
     EndLoc = findEndLocation(*S, SM, LangOpts);
     ClosingInsertion = "\n}";
   }

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 71ddb9bcbe497..53d28b439c97b 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -672,6 +672,11 @@ Changes in existing checks
   false positives when a class is seen through both a header include and
   a C++20 module import.
 
+- Improved :doc:`readability-braces-around-statements
+  <clang-tidy/checks/readability/braces-around-statements>` check by fixing a
+  crash when diagnosing a statement that ends in the middle of a macro body
+  expansion.
+
 - Improved :doc:`readability-container-size-empty
   <clang-tidy/checks/readability/container-size-empty>` check:
 

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements-same-line.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements-same-line.cpp
index 50456c6de0c89..0b2cf6e3fb072 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements-same-line.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements-same-line.cpp
@@ -2,6 +2,10 @@
 
 void do_something(const char *) {}
 
+#define BAD_MACRO(x) \
+  do_something(x);   \
+  do_something(x)
+
 bool cond(const char *) {
   return false;
 }
@@ -33,4 +37,8 @@ void test() {
   // CHECK-MESSAGES: :[[@LINE-7]]:31: warning: statement should be inside braces
   // CHECK-FIXES: if (cond("if4") /*comment*/) {
   // CHECK-FIXES: }
+
+  if (cond("macro"))
+    BAD_MACRO("macro");
+  // CHECK-MESSAGES: :[[@LINE-2]]:21: warning: statement should be inside braces
 }

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements.cpp
index f1bb4ed988d7d..6f15500040905 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/braces-around-statements.cpp
@@ -415,6 +415,14 @@ int test_macros(bool b) {
   // CHECK-FIXES-NEXT: do_something("for in wrapping macro 3")
   // CHECK-FIXES-NEXT: );
 
+  #define BAD_MACRO(x) \
+    do_something(x);   \
+    do_something(x)
+
+  if (b)
+    BAD_MACRO("macro body");
+  // CHECK-MESSAGES: :[[@LINE-2]]:9: warning: statement should be inside braces
+
   // Taken from https://bugs.llvm.org/show_bug.cgi?id=22785
   int i;
   #define MACRO_1 i++