improved regex matching, updated docs

Author: balazske

clang-tools-extra/clang-tidy/bugprone/CastToStructCheck.cpp

@@ -18,7 +18,11 @@ namespace clang::tidy::bugprone {
 CastToStructCheck::CastToStructCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
       IgnoredCasts(
-          utils::options::parseStringList(Options.get("IgnoredCasts", ""))) {}
+          utils::options::parseStringList(Options.get("IgnoredCasts", ""))) {
+  IgnoredCastsRegex.reserve(IgnoredCasts.size());
+  for (const auto &Str : IgnoredCasts)
+    IgnoredCastsRegex.emplace_back(Str);
+}
 
 void CastToStructCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "IgnoredCasts",
@@ -60,14 +64,12 @@ void CastToStructCheck::check(const MatchFinder::MatchResult &Result) {
 
   const std::string FromName = FromPointee->getAsString();
   const std::string ToName = ToPointee->getAsString();
-  llvm::Regex FromR;
-  llvm::Regex ToR;
-  for (auto [Idx, Str] : llvm::enumerate(IgnoredCasts)) {
+  bool FromMatch = false;
+  for (auto [Idx, Regex] : llvm::enumerate(IgnoredCastsRegex)) {
     if (Idx % 2 == 0) {
-      FromR = llvm::Regex(Str);
+      FromMatch = Regex.match(FromName);
     } else {
-      ToR = llvm::Regex(Str);
-      if (FromR.match(FromName) && ToR.match(ToName))
+      if (FromMatch && Regex.match(ToName))
         return;
     }
   }

clang-tools-extra/clang-tidy/bugprone/CastToStructCheck.h

@@ -30,6 +30,7 @@ class CastToStructCheck : public ClangTidyCheck {
 
 private:
   std::vector<llvm::StringRef> IgnoredCasts;
+  std::vector<llvm::Regex> IgnoredCastsRegex;
 };
 
 } // namespace clang::tidy::bugprone

clang-tools-extra/docs/clang-tidy/checks/bugprone/cast-to-struct.rst

@@ -52,9 +52,16 @@ Options
    types to ignore. The list should contain pairs of type names in a way that
    the first type is the "from" type, the second is the "to" type in a cast
    expression. The types in a pair and the pairs itself are separated by
-   `;` characters. For example `char;Type1;char;Type2` specifies that the
-   check does not produce warning for casts from ``char *`` to ``Type1 *`` and
-   casts from ``char *`` to ``Type2 *``. The list entries can be regular
-   expressions. The type name in the cast expression is matched without
-   resolution of type aliases like ``typedef``. Default value is empty list.
-   (Casts from ``void *`` are ignored always regardless of this list.)
+   `;` characters. For example `char;struct Type1;char;struct Type2` specifies
+   that the check does not produce warning for casts from ``char *`` to
+   ``struct Type1 *`` and casts from ``char *`` to ``struct Type2 *`` (the `*`
+   character to indicate pointer should not be used in the list). The type name
+   in the cast expression is matched without resolution of type aliases like
+   ``typedef``.
+   
+   The list entries are matched as substring regular expressions. For example
+   `char` would match `unsigned char` too. This problem can be avoided by using
+   anchor characters (`^char$`).
+   
+   Default value of the option is an empty list. (Casts from ``void *`` are
+   ignored always regardless of this list.)

clang-tools-extra/test/clang-tidy/checkers/bugprone/cast-to-struct-ignore.c

@@ -1,5 +1,5 @@
 // RUN: %check_clang_tidy %s bugprone-cast-to-struct %t -- \
-// RUN:   -config="{CheckOptions: {bugprone-cast-to-struct.IgnoredCasts: 'char;S1;int;Other*'}}"
+// RUN:   -config="{CheckOptions: {bugprone-cast-to-struct.IgnoredCasts: '^char$;^struct S1$;^int$;Other'}}"
 
 struct S1 {
   int a;
@@ -9,7 +9,7 @@ struct S2 {
   char a;
 };
 
-struct OtherS {
+struct SomeOtherS {
   int a;
   int b;
 };
@@ -22,10 +22,10 @@ void test1(char *p1, int *p2) {
   // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: casting a 'char *' pointer to a 'struct S2 *'
   s2 = (struct S2 *)p2;
   // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: casting a 'int *' pointer to a 'struct S2 *'
-  struct OtherS *s3;
-  s3 = (struct OtherS *)p2;
-  s3 = (struct OtherS *)p1;
-  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: casting a 'char *' pointer to a 'struct OtherS *'
+  struct SomeOtherS *s3;
+  s3 = (struct SomeOtherS *)p2;
+  s3 = (struct SomeOtherS *)p1;
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: casting a 'char *' pointer to a 'struct SomeOtherS *'
 }
 
 struct S2 *test_void_is_always_ignored(void *p) {