[clang-tools-extra] 1219cc7 - [clang-tidy] Warn on use of std::get_temporary_buffer (#176191)

[via cfe-commits]

Author: Donát Nagy
Date: 2026-01-19T17:56:24+01:00
New Revision: 1219cc76d13825e060c4c7eb133a430abe2d5f7e

URL: https://github.com/llvm/llvm-project/commit/1219cc76d13825e060c4c7eb133a430abe2d5f7e
DIFF: https://github.com/llvm/llvm-project/commit/1219cc76d13825e060c4c7eb133a430abe2d5f7e.diff

LOG: [clang-tidy] Warn on use of std::get_temporary_buffer (#176191)

The STL function `std::get_temporary_buffer` was originally designed
with the intent of providing a more efficient implementation than the
general-purpose operator new, but no such implementation was created and
the API was deprecated (in C++17) and removed (in C++20).

As this function is difficult to use and provides no advantages, I think
(or at least hope) that nobody actually uses it; but given that it was
present in the official standard, I think tidy should be able to report
its bugprone nature. (It returns uninitialized memory, which can cause
subtle bugs, e.g. as in the last code example of the SEI CERT rule
EXP54-CPP.)

Added: 
    clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions.cpp

Modified: 
    clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/docs/clang-tidy/checks/bugprone/unsafe-functions.rst

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
index dc749924fb700..6694356a2be98 100644
--- a/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/UnsafeFunctionsCheck.cpp
@@ -60,7 +60,8 @@ static StringRef getReplacementFor(StringRef FunctionName,
       .Cases({"asctime", "asctime_r"}, "strftime")
       .Case("gets", "fgets")
       .Case("rewind", "fseek")
-      .Case("setbuf", "setvbuf");
+      .Case("setbuf", "setvbuf")
+      .Case("get_temporary_buffer", "operator new[]");
 }
 
 static StringRef getReplacementForAdditional(StringRef FunctionName,
@@ -97,6 +98,9 @@ static StringRef getRationaleFor(StringRef FunctionName) {
       .Cases({"rewind", "setbuf"}, "has no error detection")
       .Case("vfork", "is insecure as it can lead to denial of service "
                      "situations in the parent process")
+      .Case("get_temporary_buffer", "returns uninitialized memory without "
+                                    "performance advantages, was deprecated in "
+                                    "C++17 and removed in C++20")
       .Default("is not bounds-checking");
 }
 
@@ -221,7 +225,8 @@ void UnsafeFunctionsCheck::registerMatchers(MatchFinder *Finder) {
 
     // Matching functions with replacements without Annex K.
     auto FunctionNamesMatcher =
-        hasAnyName("::asctime", "asctime_r", "::gets", "::rewind", "::setbuf");
+        hasAnyName("::asctime", "asctime_r", "::gets", "::rewind", "::setbuf",
+                   "::std::get_temporary_buffer");
     Finder->addMatcher(
         declRefExpr(
             to(functionDecl(FunctionNamesMatcher).bind(FunctionNamesId)))

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 68293fcdfafe2..4a44f3db9ac03 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -103,6 +103,11 @@ New check aliases
 Changes in existing checks
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Improved :doc:`bugprone-unsafe-functions
+  <clang-tidy/checks/bugprone/unsafe-functions>` check by adding the function
+  ``std::get_temporary_buffer`` to the default list of unsafe functions. (This
+  function is unsafe, useless, deprecated in C++17 and removed in C++20).
+
 - Improved :doc:`misc-const-correctness
   <clang-tidy/checks/misc/const-correctness>` check:
 

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 aaf7aaff4a05c..4f5f8b39ed406 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
@@ -48,6 +48,8 @@ availability:
 
  - ``rewind``, suggested replacement: ``fseek``
  - ``setbuf``, suggested replacement: ``setvbuf``
+ - ``std::get_temporary_buffer``, suggested replacement: "plain" allocation
+   with ``operator new[]``
 
 If :option:`ReportMoreUnsafeFunctions` is enabled,
 the following functions are also checked:

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions.cpp
new file mode 100644
index 0000000000000..1ff04ed002a92
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/unsafe-functions.cpp
@@ -0,0 +1,20 @@
+// RUN: %check_clang_tidy -std=c++11-or-later %s bugprone-unsafe-functions %t --
+
+namespace std {
+template <class T1, class T2>
+struct pair {
+  T1 first;
+  T2 second;
+};
+
+using ptr
diff _t = long long;
+
+template<class T>
+std::pair<T*, std::ptr
diff _t>
+    get_temporary_buffer(std::ptr
diff _t count) noexcept;
+}
+
+void test() {
+  (void)std::get_temporary_buffer<int>(64);
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: function 'get_temporary_buffer<int>' returns uninitialized memory without performance advantages, was deprecated in C++17 and removed in C++20; 'operator new[]' should be used instead
+}