[clang-tools-extra] [clang-tidy] Ignore parameters of `main` in `misc-const-correctness` (PR #228120)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tools-extra

Author: David Meng (davidmenggx)

<details>
<summary>Changes</summary>

The standard fixes the signature of `main`, so suggesting `const` for its parameters is a false positive. The check warned on `char **argv` but not on `char *argv[]`. The array form did not warn because the check does not analyze array-style parameters.

The check now skips all parameters of `main`. Local variables inside `main` are still checked.

Fixes https://github.com/llvm/llvm-project/issues/227988

---
Full diff: https://github.com/llvm/llvm-project/pull/228120.diff


4 Files Affected:

- (modified) clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp (+2-2) 
- (modified) clang-tools-extra/docs/ReleaseNotes.md (+3) 
- (modified) clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst (+2-2) 
- (added) clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-parameters-main.cpp (+23) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp b/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
index 57c2bda6c3fd5..90919555d447e 100644
--- a/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
@@ -191,8 +191,8 @@ void ConstCorrectnessCheck::registerMatchers(MatchFinder *Finder) {
     const auto FunctionWithParams =
         functionDecl(
             hasBody(stmt().bind("scope")), has(typeLoc(forEach(ParamMatcher))),
-            unless(cxxMethodDecl()), unless(isFunctionTemplateSpecialization()),
-            unless(isTemplate()))
+            unless(cxxMethodDecl()), unless(isMain()),
+            unless(isFunctionTemplateSpecialization()), unless(isTemplate()))
             .bind("function-decl");
 
     Finder->addMatcher(FunctionWithParams, this);
diff --git a/clang-tools-extra/docs/ReleaseNotes.md b/clang-tools-extra/docs/ReleaseNotes.md
index c2ee1b06c43e0..41aa783cabd24 100644
--- a/clang-tools-extra/docs/ReleaseNotes.md
+++ b/clang-tools-extra/docs/ReleaseNotes.md
@@ -218,6 +218,9 @@ infrastructure are described first, followed by tool-specific sections.
   - No longer diagnoses variables declared with `decltype(auto)`, where the
     suggested `const` does not compile.
     
+  - No longer diagnoses parameters of `main`, whose signature is fixed by the
+    standard.
+
 - Fixed an infinite loop in {doc}`misc-multiple-inheritance
   <clang-tidy/checks/misc/multiple-inheritance>` when checking a class that
   inherits from itself or has a circular inheritance graph.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst b/clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst
index ce699e06b9276..0a1eaf0e45a57 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst
@@ -122,8 +122,8 @@ Options
 
   Enable or disable the analysis of function parameters, like
   ``void foo(int* ptr)``. Only reference and pointer parameters are analyzed.
-  Unnamed parameters, member functions (including constructors) and lambdas are
-  excluded from the analysis. Default is `true`.
+  Unnamed parameters, parameters of ``main``, member functions (including
+  constructors) and lambdas are excluded from the analysis. Default is `true`.
 
   .. code-block:: c++
 
diff --git a/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-parameters-main.cpp b/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-parameters-main.cpp
new file mode 100644
index 0000000000000..9582ed892b734
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-parameters-main.cpp
@@ -0,0 +1,23 @@
+// RUN: %check_clang_tidy %s misc-const-correctness %t \
+// RUN: -config='{CheckOptions: {misc-const-correctness.WarnPointersAsValues: true}}'
+// RUN: %check_clang_tidy %s misc-const-correctness %t \
+// RUN: -config='{CheckOptions: {misc-const-correctness.WarnPointersAsValues: true}}' \
+// RUN: -- -DARRAY_SYNTAX
+
+namespace ns {
+int main(int argc, char **argv) {
+  // CHECK-MESSAGES: :[[@LINE-1]]:20: warning: pointee of variable 'argv' of type 'char **' can be declared 'const'
+  // CHECK-MESSAGES: :[[@LINE-2]]:20: warning: variable 'argv' of type 'char **' can be declared 'const'
+  return 0;
+}
+} // namespace ns
+
+#ifdef ARRAY_SYNTAX
+int main(int argc, char *argv[], char *envp[]) {
+#else
+int main(int argc, char **argv, char **envp) {
+#endif
+  int n = argc;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: variable 'n' of type 'int' can be declared 'const'
+  return n;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/228120