https://github.com/filaka771 updated https://github.com/llvm/llvm-project/pull/203792
>From 0fd336cfa52938b1af10eced6b71d6895f063afd Mon Sep 17 00:00:00 2001 From: Alex Filak <[email protected]> Date: Sun, 14 Jun 2026 00:40:00 +0300 Subject: [PATCH 1/4] [clang] Fix char-array constant-conversion suppression --- clang/lib/Sema/SemaChecking.cpp | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp index b8a3f48a32f24..80e8f6cc7e540 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -13080,7 +13080,8 @@ static void DiagnoseNullConversion(Sema &S, Expr *E, QualType T, } // Helper function to filter out cases for constant width constant conversion. -// Don't warn on char array initialization or for non-decimal values. +// Don't warn on char / unsigned char array initialization or for non-decimal +// values. static bool isSameWidthConstantConversion(Sema &S, Expr *E, QualType T, SourceLocation CC) { // If initializing from a constant, and the constant starts with '0', @@ -13093,12 +13094,16 @@ static bool isSameWidthConstantConversion(Sema &S, Expr *E, QualType T, return false; } - // If the CC location points to a '{', and the type is char, then assume - // assume it is an array initialization. + // If the CC location points to a '{', and the destination type is char or + // unsigned char, then assume this is an array initialization. Keep warning + // for signed char arrays, where values such as 255 change sign. if (CC.isValid() && T->isCharType()) { + const auto *BT = + dyn_cast<BuiltinType>(S.Context.getCanonicalType(T).getTypePtr()); const char FirstContextCharacter = S.getSourceManager().getCharacterData(CC)[0]; - if (FirstContextCharacter == '{') + if (BT && BT->getKind() != BuiltinType::SChar && + FirstContextCharacter == '{') return false; } >From c6d583a1589e031e9e3850ebaff17f6df48f5a93 Mon Sep 17 00:00:00 2001 From: Alex Filak <[email protected]> Date: Sun, 14 Jun 2026 00:40:12 +0300 Subject: [PATCH 2/4] [clang] Add char-array constant-conversion tests --- clang/test/Sema/constant-conversion.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/clang/test/Sema/constant-conversion.c b/clang/test/Sema/constant-conversion.c index ffc25b9cc4978..b40379e2180ce 100644 --- a/clang/test/Sema/constant-conversion.c +++ b/clang/test/Sema/constant-conversion.c @@ -125,6 +125,16 @@ void test9(void) { char macro_char_dec = CHAR_MACRO_DEC; // expected-warning {{implicit conversion from 'int' to 'char' changes value from 255 to -1}} char array_init[] = { 255, 127, 128, 129, 0 }; + unsigned char unsigned_array_init[] = { 255 }; + unsigned char unsigned_array_init_multi[] = { 255, 127, 128, 129, 0 }; + signed char signed_array_init[] = { 255 }; // expected-warning {{implicit conversion from 'int' to 'signed char' changes value from 255 to -1}} + signed char signed_array_init_multi[] = { + 255, // expected-warning {{implicit conversion from 'int' to 'signed char' changes value from 255 to -1}} + 127, + 128, // expected-warning {{implicit conversion from 'int' to 'signed char' changes value from 128 to -128}} + 129, // expected-warning {{implicit conversion from 'int' to 'signed char' changes value from 129 to -127}} + 0 + }; } #define A 1 >From 4ee5bb5751469133b4790888b39c04e7348537db Mon Sep 17 00:00:00 2001 From: Alex Filak <[email protected]> Date: Wed, 17 Jun 2026 21:53:22 +0300 Subject: [PATCH 3/4] [clang] Add release note for signed-char array warning --- clang/docs/ReleaseNotes.rst | 2 ++ 1 file changed, 2 insertions(+) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 11656d560ee34..b33faad2ab6b9 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -646,6 +646,8 @@ Improvements to Clang's diagnostics - Diagnostics for the C++11 range-based for statement now report the correct iterator type in notes for invalid iterator types. +- Fixed a missing ``-Wconstant-conversion`` diagnostic for ``signed char`` array initialization. + Improvements to Clang's time-trace ---------------------------------- >From 4e26791ee041bb35f9b72f0ad3abb181ea3ec5ee Mon Sep 17 00:00:00 2001 From: Alex Filak <[email protected]> Date: Fri, 26 Jun 2026 07:02:08 +0300 Subject: [PATCH 4/4] [clang] Handle plain char signedness in array conversion warnings --- clang/docs/ReleaseNotes.rst | 3 ++- clang/lib/Sema/SemaChecking.cpp | 13 +++++++------ clang/test/Sema/constant-conversion.c | 17 ++++++++++++----- 3 files changed, 21 insertions(+), 12 deletions(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index b33faad2ab6b9..5c97d00d084f0 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -646,7 +646,8 @@ Improvements to Clang's diagnostics - Diagnostics for the C++11 range-based for statement now report the correct iterator type in notes for invalid iterator types. -- Fixed a missing ``-Wconstant-conversion`` diagnostic for ``signed char`` array initialization. +- Fixed a missing ``-Wconstant-conversion`` diagnostic for ``signed char`` + array initialization. (#GH181730) Improvements to Clang's time-trace ---------------------------------- diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp index 80e8f6cc7e540..b381975cd45ab 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -13080,8 +13080,8 @@ static void DiagnoseNullConversion(Sema &S, Expr *E, QualType T, } // Helper function to filter out cases for constant width constant conversion. -// Don't warn on char / unsigned char array initialization or for non-decimal -// values. +// Don't warn on unsigned char / unsigned plain char array initialization or for +// non-decimal values. static bool isSameWidthConstantConversion(Sema &S, Expr *E, QualType T, SourceLocation CC) { // If initializing from a constant, and the constant starts with '0', @@ -13094,16 +13094,17 @@ static bool isSameWidthConstantConversion(Sema &S, Expr *E, QualType T, return false; } - // If the CC location points to a '{', and the destination type is char or - // unsigned char, then assume this is an array initialization. Keep warning - // for signed char arrays, where values such as 255 change sign. + // If the CC location points to a '{', and the destination type is plain char + // with unsigned signedness or unsigned char, then assume this is an array + // initialization. Keep warning for signed char arrays and plain char arrays + // with signed signedness, where values such as 255 change sign. if (CC.isValid() && T->isCharType()) { const auto *BT = dyn_cast<BuiltinType>(S.Context.getCanonicalType(T).getTypePtr()); const char FirstContextCharacter = S.getSourceManager().getCharacterData(CC)[0]; if (BT && BT->getKind() != BuiltinType::SChar && - FirstContextCharacter == '{') + BT->getKind() != BuiltinType::Char_S && FirstContextCharacter == '{') return false; } diff --git a/clang/test/Sema/constant-conversion.c b/clang/test/Sema/constant-conversion.c index b40379e2180ce..31e378eb707cc 100644 --- a/clang/test/Sema/constant-conversion.c +++ b/clang/test/Sema/constant-conversion.c @@ -1,5 +1,6 @@ -// RUN: %clang_cc1 -fsyntax-only -ffreestanding -verify=expected,one-bit -triple x86_64-apple-darwin %s -// RUN: %clang_cc1 -fsyntax-only -ffreestanding -Wno-single-bit-bitfield-constant-conversion -verify -triple x86_64-apple-darwin %s +// RUN: %clang_cc1 -fsyntax-only -ffreestanding -verify=expected,signed-plain-char,one-bit -triple x86_64-apple-darwin %s +// RUN: %clang_cc1 -fsyntax-only -ffreestanding -Wno-single-bit-bitfield-constant-conversion -verify=expected,signed-plain-char -triple x86_64-apple-darwin %s +// RUN: %clang_cc1 -fsyntax-only -ffreestanding -Wno-single-bit-bitfield-constant-conversion -verify=expected,unsigned-plain-char -triple x86_64-apple-darwin -fno-signed-char %s #include <stdbool.h> @@ -103,7 +104,7 @@ void test9(void) { const int max_short_plus_one = (int)max_short + 1; const long max_int_plus_one = (long)max_int + 1; - char new_char = max_char_plus_one; // expected-warning {{implicit conversion from 'const short' to 'char' changes value from 128 to -128}} + char new_char = max_char_plus_one; // signed-plain-char-warning {{implicit conversion from 'const short' to 'char' changes value from 128 to -128}} short new_short = max_short_plus_one; // expected-warning {{implicit conversion from 'const int' to 'short' changes value from 32768 to -32768}} int new_int = max_int_plus_one; // expected-warning {{implicit conversion from 'const long' to 'int' changes value from 2147483648 to -2147483648}} @@ -122,9 +123,15 @@ void test9(void) { #define CHAR_MACRO_HEX 0xff char macro_char_hex = CHAR_MACRO_HEX; #define CHAR_MACRO_DEC 255 - char macro_char_dec = CHAR_MACRO_DEC; // expected-warning {{implicit conversion from 'int' to 'char' changes value from 255 to -1}} + char macro_char_dec = CHAR_MACRO_DEC; // signed-plain-char-warning {{implicit conversion from 'int' to 'char' changes value from 255 to -1}} - char array_init[] = { 255, 127, 128, 129, 0 }; + char array_init[] = { + 255, // signed-plain-char-warning {{implicit conversion from 'int' to 'char' changes value from 255 to -1}} + 127, + 128, // signed-plain-char-warning {{implicit conversion from 'int' to 'char' changes value from 128 to -128}} + 129, // signed-plain-char-warning {{implicit conversion from 'int' to 'char' changes value from 129 to -127}} + 0 + }; unsigned char unsigned_array_init[] = { 255 }; unsigned char unsigned_array_init_multi[] = { 255, 127, 128, 129, 0 }; signed char signed_array_init[] = { 255 }; // expected-warning {{implicit conversion from 'int' to 'signed char' changes value from 255 to -1}} _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
