[clang-tools-extra] [clang-tidy] Add a fully custom message to `bugprone-unsafe-functions` (PR #162443)

[via cfe-commits]

https://github.com/Discookie updated https://github.com/llvm/llvm-project/pull/162443

>From 2bd457b5424fa8138f8c991a4e520b6b3778c56f Mon Sep 17 00:00:00 2001
From: Viktor <viktor.cseh at ericsson.com>
Date: Wed, 8 Oct 2025 08:48:30 +0000
Subject: [PATCH] [clang-tidy] Add a fully custom message to
 `bugprone-unsafe-functions`

In some cases, such as when recommending the compiler option _FORTIFY_SOURCE, the current custom message format is clunky.
Now, when the reason starts with `>`, the replacement string is omitted., so only the Reason is shown.
---
 .../clang-tidy/bugprone/UnsafeFunctionsCheck.cpp          | 8 +++++++-
 clang-tools-extra/docs/ReleaseNotes.rst                   | 5 +++++
 .../docs/clang-tidy/checks/bugprone/unsafe-functions.rst  | 7 ++++++-
 .../checkers/bugprone/unsafe-functions-custom.c           | 6 +++---
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
index 0399af2a673f4..d24b4998b8bd7 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
@@ -304,11 +304,17 @@ void UnsafeFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
         StringRef Reason =
             Entry.Reason.empty() ? "is marked as unsafe" : Entry.Reason.c_str();
 
-        if (Entry.Replacement.empty()) {
+        // Omit the replacement, when a fully-custom reason is given.
+        if (Reason.consume_front(">")) {
+          diag(SourceExpr->getExprLoc(), "function %0 %1")
+              << FuncDecl << Reason.trim() << SourceExpr->getSourceRange();
+          // Do not recommend a replacement when it is not present.
+        } else if (Entry.Replacement.empty()) {
           diag(SourceExpr->getExprLoc(),
                "function %0 %1; it should not be used")
               << FuncDecl << Reason << Entry.Replacement
               << SourceExpr->getSourceRange();
+          // Otherwise, emit the replacement.
         } else {
           diag(SourceExpr->getExprLoc(),
                "function %0 %1; '%2' should be used instead")
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 4197abac273b0..e154522a0d946 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -299,6 +299,11 @@ Changes in existing checks
   an additional matcher that generalizes the copy-and-swap idiom pattern
   detection.
 
+- Improved :doc:`bugprone-unsafe-functions
+  <clang-tidy/checks/bugprone/unsafe-functions>` check by omitting the custom 
+  replacement string, when the Reason starts with the character `>` in the
+  `CustomFunctions` option.
+
 - Improved :doc:`cppcoreguidelines-prefer-member-initializer
   <clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>` check to
   avoid false positives on inherited members in class templates.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst b/clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst
index 317db9c5564e2..af6d59fe5c0b4 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst
@@ -98,7 +98,9 @@ The `reason` is optional and is used to provide additional information about the
 reasoning behind the replacement. The default reason is `is marked as unsafe`.
 
 If `replacement` is empty, the text `it should not be used` will be shown
-instead of the suggestion for a replacement.
+instead of the suggestion for a replacement. If the `reason` starts with the
+character `>`, the replacement message is disabled, to allow better control over
+the suggestions.
 
 As an example, the configuration `^original$, replacement, is deprecated;`
 will produce the following diagnostic message.
@@ -114,6 +116,9 @@ qualified name (i.e. ``std::original``), otherwise the regex is matched against
 If the regular expression starts with `::` (or `^::`), it is matched against the
 fully qualified name (``::std::original``).
 
+A similar diagnostic message can be printed with the cofiguration
+`^original$,,> is deprecated, 'replacement' should be used instead`.
+
 .. note::
 
    Fully qualified names can contain template parameters on certain C++ classes, but not on C++ functions.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions-custom.c b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions-custom.c
index 7fd71ec2f2e7b..7eaf015f06aa2 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions-custom.c
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions-custom.c
@@ -1,5 +1,5 @@
 // RUN: %check_clang_tidy -check-suffix=NON-STRICT-REGEX %s bugprone-unsafe-functions %t --\
-// RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: '::name_match,replacement,is a qualname match;^::prefix_match,,is matched on qualname prefix'}}"
+// RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: \"::name_match,,>is a qualname match, but with a fully 'custom' message;^::prefix_match,,is matched on qualname prefix\"}}"
 // RUN: %check_clang_tidy -check-suffix=STRICT-REGEX     %s bugprone-unsafe-functions %t --\
 // RUN:   -config="{CheckOptions: {bugprone-unsafe-functions.CustomFunctions: '^name_match$,replacement,is matched on function name only;^::prefix_match$,,is a full qualname match'}}"
 
@@ -11,14 +11,14 @@ void prefix_match_regex();
 
 void f1() {
   name_match();
-  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'name_match' is a qualname match; 'replacement' should be used instead
+  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'name_match' is a qualname match, but with a fully 'custom' message
   // CHECK-MESSAGES-STRICT-REGEX: :[[@LINE-2]]:3: warning: function 'name_match' is matched on function name only; 'replacement' should be used instead
   prefix_match();
   // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'prefix_match' is matched on qualname prefix; it should not be used
   // CHECK-MESSAGES-STRICT-REGEX: :[[@LINE-2]]:3: warning: function 'prefix_match' is a full qualname match; it should not be used
 
   name_match_regex();
-  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'name_match_regex' is a qualname match; 'replacement' should be used instead
+  // CHECK-MESSAGES-NON-STRICT-REGEX: :[[@LINE-1]]:3: warning: function 'name_match_regex' is a qualname match, but with a fully 'custom' message
   // no-warning STRICT-REGEX
 
   prefix_match_regex();