https://github.com/filaka771 updated https://github.com/llvm/llvm-project/pull/203792
>From f8eb7ae6127aa00c441f4f9e6242be9290449edb 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 ef07e8c6133ed..24914c0057c7b 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -13251,7 +13251,8 @@ 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', @@ -13264,12 +13265,16 @@ 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 ab55b35b3edabca58ae31cd2b2a93b4cf31da3fc 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 1e6ec0df823dccd6a9eed9fe4697833bfb9d962f 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.md | 3 +++ 1 file changed, 3 insertions(+) diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md index 3dd17d8c523bc..3b2dce7a2fa2e 100644 --- a/clang/docs/ReleaseNotes.md +++ b/clang/docs/ReleaseNotes.md @@ -325,6 +325,9 @@ features cannot lower the translation-unit ABI level; - Clang now attempts to print enumerator names rather than C-style cast expressions in more diagnostics. +- Fixed a missing `-Wconstant-conversion` diagnostic for `signed char` array + initialization. + ### Improvements to Clang's time-trace >From e5c5b146eecdf8af9f7649b45e69e6d3628bf0b8 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.md | 3 +-- clang/lib/Sema/SemaChecking.cpp | 14 +++++--------- clang/test/Sema/constant-conversion.c | 11 ++++++----- 3 files changed, 12 insertions(+), 16 deletions(-) diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md index 3b2dce7a2fa2e..dc7b9f7b17143 100644 --- a/clang/docs/ReleaseNotes.md +++ b/clang/docs/ReleaseNotes.md @@ -326,8 +326,7 @@ features cannot lower the translation-unit ABI level; in more diagnostics. - Fixed a missing `-Wconstant-conversion` diagnostic for `signed char` array - initialization. - + initialization. (#GH181730) ### Improvements to Clang's time-trace diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp index 24914c0057c7b..debf1a8198b63 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -13251,7 +13251,7 @@ 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 +// Don't warn on unsigned character array initialization or for non-decimal // values. static bool isSameWidthConstantConversion(Sema &S, Expr *E, QualType T, SourceLocation CC) { @@ -13265,16 +13265,12 @@ 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 (CC.isValid() && T->isCharType()) { - const auto *BT = - dyn_cast<BuiltinType>(S.Context.getCanonicalType(T).getTypePtr()); + // If the CC location points to a '{' and the type is an unsigned character + // type, assume it is an array initialization. + if (T->isCharType() && !T->isSignedIntegerType() && CC.isValid()) { const char FirstContextCharacter = S.getSourceManager().getCharacterData(CC)[0]; - if (BT && BT->getKind() != BuiltinType::SChar && - FirstContextCharacter == '{') + if (FirstContextCharacter == '{') return false; } diff --git a/clang/test/Sema/constant-conversion.c b/clang/test/Sema/constant-conversion.c index b40379e2180ce..adba3315cc9b4 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 -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 +123,9 @@ 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}} 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
