[clang-tools-extra] 36af073 - Accept string literal decay in conditional operator

[Aaron Ballman via cfe-commits]

Author: Elvis Stansvik
Date: 2022-01-11T15:05:30-05:00
New Revision: 36af07334246a87a0f3fb9bbc85dedfca04b00d1

URL: https://github.com/llvm/llvm-project/commit/36af07334246a87a0f3fb9bbc85dedfca04b00d1
DIFF: https://github.com/llvm/llvm-project/commit/36af07334246a87a0f3fb9bbc85dedfca04b00d1.diff

LOG: Accept string literal decay in conditional operator

The cppcoreguidelines-pro-bounds-array-to-pointer-decay check currently
accepts:

const char *b = i ? "foo" : "foobar";

but not

const char *a = i ? "foo" : "bar";

This is because the AST is slightly different in the latter case (see
https://godbolt.org/z/MkHVvs).

This eliminates the inconsistency by making it accept the latter form
as well.

Fixes https://github.com/llvm/llvm-project/issues/31155.

Added: 
    

Modified: 
    clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
index 160d15e6c0e1f..ba9c64ec16a8d 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/ProBoundsArrayToPointerDecayCheck.cpp
@@ -54,13 +54,17 @@ void ProBoundsArrayToPointerDecayCheck::registerMatchers(MatchFinder *Finder) {
   // 2) inside a range-for over an array
   // 3) if it converts a string literal to a pointer
   Finder->addMatcher(
-      traverse(TK_AsIs,
-               implicitCastExpr(
-                   unless(hasParent(arraySubscriptExpr())),
-                   unless(hasParentIgnoringImpCasts(explicitCastExpr())),
-                   unless(isInsideOfRangeBeginEndStmt()),
-                   unless(hasSourceExpression(ignoringParens(stringLiteral()))))
-                   .bind("cast")),
+      traverse(
+          TK_AsIs,
+          implicitCastExpr(
+              unless(hasParent(arraySubscriptExpr())),
+              unless(hasParentIgnoringImpCasts(explicitCastExpr())),
+              unless(isInsideOfRangeBeginEndStmt()),
+              unless(hasSourceExpression(ignoringParens(stringLiteral()))),
+              unless(hasSourceExpression(ignoringParens(conditionalOperator(
+                  allOf(hasTrueExpression(stringLiteral()),
+                        hasFalseExpression(stringLiteral())))))))
+              .bind("cast")),
       this);
 }
 

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 03a52fa7c7aec..769eb2ba08038 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -67,6 +67,10 @@ The improvements are...
 Improvements to clang-tidy
 --------------------------
 
+- Make the `cppcoreguidelines-pro-bounds-array-to-pointer-decay` check accept
+  string literal to pointer decay in conditional operator even if operands are
+  of the same length.
+
 - Ignore warnings from macros defined in system headers, if not using the
   `-system-headers` flag.
 

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp
index 2287e48a4fe79..d41f54b4e77f2 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-bounds-array-to-pointer-decay.cpp
@@ -49,3 +49,14 @@ void bug25362() {
   void *a[2];
   f2(static_cast<void *const*>(a)); // OK, explicit cast
 }
+
+void issue31155(int i) {
+  const char *a = i ? "foo" : "bar";    // OK, decay string literal to pointer
+  const char *b = i ? "foo" : "foobar"; // OK, decay string literal to pointer
+
+  char arr[1];
+  const char *c = i ? arr : "bar";
+  // CHECK-MESSAGES: :[[@LINE-1]]:23: warning: do not implicitly decay an array into a pointer
+  const char *d = i ? "foo" : arr;
+  // CHECK-MESSAGES: :[[@LINE-1]]:31: warning: do not implicitly decay an array into a pointer
+}