[clang] [clang] Don't crash when -Wformat-signedness specified (PR #162049)
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Mon Oct 6 19:30:35 PDT 2025
https://github.com/yicuixi updated https://github.com/llvm/llvm-project/pull/162049
>From 8b4a0aca6bf77d1c61cd32f160251185d8832d72 Mon Sep 17 00:00:00 2001
From: yicuixi <qin_17914 at 126.com>
Date: Mon, 6 Oct 2025 17:07:38 +0800
Subject: [PATCH 1/2] [clang] Don't crash when -Wformat-sgnedness specified
---
clang/docs/ReleaseNotes.rst | 2 ++
clang/lib/Sema/SemaChecking.cpp | 4 ++-
clang/test/Sema/format-strings-signedness.cpp | 30 +++++++++++++++++++
3 files changed, 35 insertions(+), 1 deletion(-)
create mode 100644 clang/test/Sema/format-strings-signedness.cpp
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 46d56bb3f07f5..7952cbcad0dfc 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -366,6 +366,7 @@ Bug Fixes in This Version
- Fixed an assertion when an improper use of the ``malloc`` attribute targeting
a function without arguments caused us to try to access a non-existent argument.
(#GH159080)
+- Fixed clang crash that caused by missing diagnostic argument. (#GH161072)
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -417,6 +418,7 @@ Bug Fixes to C++ Support
``__builtin_addressof``, and related issues with builtin arguments. (#GH154034)
- Fix an assertion failure when taking the address on a non-type template parameter argument of
object type. (#GH151531)
+- Fix an assertion failure of format string signedness check when ``-Wformat-signedness`` (#GH161075).
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 00f40cfa910d2..91834d430c987 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -8634,8 +8634,10 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
case ArgType::Match:
case ArgType::MatchPromotion:
case ArgType::NoMatchPromotionTypeConfusion:
- case ArgType::NoMatchSignedness:
llvm_unreachable("expected non-matching");
+ case ArgType::NoMatchSignedness:
+ Diag = diag::warn_format_conversion_argument_type_mismatch_signedness;
+ break;
case ArgType::NoMatchPedantic:
Diag = diag::warn_format_conversion_argument_type_mismatch_pedantic;
break;
diff --git a/clang/test/Sema/format-strings-signedness.cpp b/clang/test/Sema/format-strings-signedness.cpp
new file mode 100644
index 0000000000000..66bf1de1ec09a
--- /dev/null
+++ b/clang/test/Sema/format-strings-signedness.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -verify -Wformat -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -verify -Wformat -Wformat-signedness %s
+
+// Verify that -Wformat-signedness alone (without -Wformat) trigger the
+// warnings. Note in gcc this will not trigger the signedness warnings as
+// -Wformat is default off in gcc.
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -verify -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -fsyntax-only -verify -Wformat-signedness %s
+
+// Verify that -Wformat-signedness warnings are not reported with only -Wformat
+// (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wformat -verify=okay %s
+
+// Verify that -Wformat-signedness with -Wno-format are not reported (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wformat-signedness -Wno-format -verify=okay %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wno-format -Wformat-signedness -verify=okay %s
+// okay-no-diagnostics
+
+// Ignore 'GCC requires a function with the 'format' attribute to be variadic'.
+#pragma GCC diagnostic ignored "-Wgcc-compat"
+namespace GH161075 {
+template <typename... Args>
+void format(const char *fmt, Args &&...args)
+ __attribute__((format(printf, 1, 2)));
+
+void do_format() {
+ bool b = false;
+ format("%hhi %hhu %hi %hu %i %u", b, b, b, b, b, b); // expected-warning {{format specifies type 'unsigned char' but the argument has type 'bool', which differs in signedness}}
+}
+} // namespace GH161075
>From 96e291f055920dedb2fd81184970cc86d1c6a532 Mon Sep 17 00:00:00 2001
From: yicuixi <qin_17914 at 126.com>
Date: Tue, 7 Oct 2025 10:29:52 +0800
Subject: [PATCH 2/2] revert add clang/docs/ReleaseNotes.rst
---
clang/docs/ReleaseNotes.rst | 45 ++++---------------------------------
1 file changed, 4 insertions(+), 41 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 9c145bdc71f05..46d56bb3f07f5 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -123,9 +123,6 @@ AST Dumping Potentially Breaking Changes
``__atomic_test_and_set(p, 0)``
-- Pretty-printing of templates with inherited (i.e. specified in a previous
- redeclaration) default arguments has been fixed.
-
Clang Frontend Potentially Breaking Changes
-------------------------------------------
- Members of anonymous unions/structs are now injected as ``IndirectFieldDecl``
@@ -145,28 +142,20 @@ What's New in Clang |release|?
C++ Language Changes
--------------------
-- A new family of builtins ``__builtin_*_synthesizes_from_spaceship`` has been added. These can be queried to know
- whether the ``<`` (``lt``), ``>`` (``gt``), ``<=`` (``le``), or ``>=`` (``ge``) operators are synthesized from a
+- A new family of builtins ``__builtin_*_synthesises_from_spaceship`` has been added. These can be queried to know
+ whether the ``<`` (``lt``), ``>`` (``gt``), ``<=`` (``le``), or ``>=`` (``ge``) operators are synthesised from a
``<=>``. This makes it possible to optimize certain facilities by using the ``<=>`` operation directly instead of
doing multiple comparisons.
C++2c Feature Support
^^^^^^^^^^^^^^^^^^^^^
-- Started the implementation of `P2686R5 <https://wg21.link/P2686R5>`_ Constexpr structured bindings.
- At this timem, references to constexpr and decomposition of *tuple-like* types are not supported
- (only arrays and aggregates are).
-
C++23 Feature Support
^^^^^^^^^^^^^^^^^^^^^
C++20 Feature Support
^^^^^^^^^^^^^^^^^^^^^
-- Clang now normalizes constraints before checking whether they are satisfied, as mandated by the standard.
- As a result, Clang no longer incorrectly diagnoses substitution failures in template arguments only
- used in concept-ids, and produces better diagnostics for satisfaction failure. (#GH61811) (#GH135190)
-
C++17 Feature Support
^^^^^^^^^^^^^^^^^^^^^
@@ -224,10 +213,6 @@ Non-comprehensive list of changes in this release
conditional memory loads from vectors. Binds to the LLVM intrinsics of the
same name.
-- Added ``__builtin_masked_gather`` and ``__builtin_masked_scatter`` for
- conditional gathering and scattering operations on vectors. Binds to the LLVM
- intrinsics of the same name.
-
- The ``__builtin_popcountg``, ``__builtin_ctzg``, and ``__builtin_clzg``
functions now accept fixed-size boolean vectors.
@@ -253,8 +238,6 @@ Non-comprehensive list of changes in this release
- ``__builtin_assume_dereferenceable`` now accepts non-constant size operands.
-- Fixed a crash when the second argument to ``__builtin_assume_aligned`` was not constant (#GH161314)
-
New Compiler Flags
------------------
- New option ``-fno-sanitize-debug-trap-reasons`` added to disable emitting trap reasons into the debug info when compiling with trapping UBSan (e.g. ``-fsanitize-trap=undefined``).
@@ -281,9 +264,6 @@ Attribute Changes in Clang
attribute, allowing the attribute to only be attached to the declaration. Prior, this would be
treated as an error where the definition and declaration would have differing types.
-- New format attributes ``gnu_printf``, ``gnu_scanf``, ``gnu_strftime`` and ``gnu_strfmon`` are added
- as aliases for ``printf``, ``scanf``, ``strftime`` and ``strfmon``. (#GH16219)
-
Improvements to Clang's diagnostics
-----------------------------------
- Added a separate diagnostic group ``-Wfunction-effect-redeclarations``, for the more pedantic
@@ -308,8 +288,7 @@ Improvements to Clang's diagnostics
"format specifies type 'unsigned int' but the argument has type 'int', which differs in signedness [-Wformat-signedness]"
"signedness of format specifier 'u' is incompatible with 'c' [-Wformat-signedness]"
and the API-visible diagnostic id will be appropriate.
-- Clang now produces better diagnostics for template template parameter matching
- involving 'auto' template parameters.
+
- Fixed false positives in ``-Waddress-of-packed-member`` diagnostics when
potential misaligned members get processed before they can get discarded.
(#GH144729)
@@ -370,7 +349,6 @@ Bug Fixes in This Version
first parameter. (#GH113323).
- Fixed a crash with incompatible pointer to integer conversions in designated
initializers involving string literals. (#GH154046)
-- Fix crash on CTAD for alias template. (#GH131342), (#GH131408)
- Clang now emits a frontend error when a function marked with the `flatten` attribute
calls another function that requires target features not enabled in the caller. This
prevents a fatal error in the backend.
@@ -388,7 +366,6 @@ Bug Fixes in This Version
- Fixed an assertion when an improper use of the ``malloc`` attribute targeting
a function without arguments caused us to try to access a non-existent argument.
(#GH159080)
-- Fixed a failed assertion with empty filename arguments in ``__has_embed``. (#GH159898)
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -440,12 +417,6 @@ Bug Fixes to C++ Support
``__builtin_addressof``, and related issues with builtin arguments. (#GH154034)
- Fix an assertion failure when taking the address on a non-type template parameter argument of
object type. (#GH151531)
-- Fix an assertion failure of format string signedness check when ``-Wformat-signedness`` (#GH161075).
-- Suppress ``-Wdouble-promotion`` when explicitly asked for with C++ list initialization (#GH33409).
-- Fix the result of `__builtin_is_implicit_lifetime` for types with a user-provided constructor. (#GH160610)
-- Correctly deduce return types in ``decltype`` expressions. (#GH160497) (#GH56652) (#GH116319) (#GH161196)
-- Fixed a crash in the pre-C++23 warning for attributes before a lambda declarator (#GH161070).
-- Fix a crash when attempting to deduce a deduction guide from a non deducible template template parameter. (#130604)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -454,11 +425,9 @@ Bug Fixes to AST Handling
legal representation. This is fixed because ElaboratedTypes don't exist anymore. (#GH43179) (#GH68670) (#GH92757)
- Fix unrecognized html tag causing undesirable comment lexing (#GH152944)
- Fix comment lexing of special command names (#GH152943)
-- Use `extern` as a hint to continue parsing when recovering from a malformed declaration.
Miscellaneous Bug Fixes
^^^^^^^^^^^^^^^^^^^^^^^
-- Fixed missing diagnostics of ``diagnose_if`` on templates involved in initialization. (#GH160776)
Miscellaneous Clang Crashes Fixed
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -561,7 +530,6 @@ clang-format
- Add ``NumericLiteralCase`` option for enforcing character case in numeric
literals.
- Add ``Leave`` suboption to ``IndentPPDirectives``.
-- Add ``AllowBreakBeforeQtProperty`` option.
libclang
--------
@@ -584,7 +552,6 @@ Crash and bug fixes
- Fixed a crash in the static analyzer that when the expression in an
``[[assume(expr)]]`` attribute was enclosed in parentheses. (#GH151529)
- Fixed a crash when parsing ``#embed`` parameters with unmatched closing brackets. (#GH152829)
-- Fixed a crash when compiling ``__real__`` or ``__imag__`` unary operator on scalar value with type promotion. (#GH160583)
Improvements
^^^^^^^^^^^^
@@ -596,13 +563,10 @@ Moved checkers
Sanitizers
----------
-- Improved documentation for legacy ``no_sanitize`` attributes.
Python Binding Changes
----------------------
-- Exposed ``clang_getCursorLanguage`` via ``Cursor.language``.
-- Add all missing ``CursorKind``s, ``TypeKind``s and
- ``ExceptionSpecificationKind``s from ``Index.h``
+- Exposed `clang_getCursorLanguage` via `Cursor.language`.
OpenMP Support
--------------
@@ -616,7 +580,6 @@ OpenMP Support
- Added support for ``defaultmap`` directive implicit-behavior ``storage``.
- Added support for ``defaultmap`` directive implicit-behavior ``private``.
- Added parsing and semantic analysis support for ``groupprivate`` directive.
-- Added support for 'omp fuse' directive.
Improvements
^^^^^^^^^^^^
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