https://github.com/ojhunt created https://github.com/llvm/llvm-project/pull/173212
The fast path for string literals fails to consider the offset of the pointer into an array of chars, this change simply adds the required checks and bounds corrections prior to calling strnlen. Fixes #173175 >From 6eff318fdc6aafb6c853e4e5fc35b34bc6d45232 Mon Sep 17 00:00:00 2001 From: Oliver Hunt <[email protected]> Date: Sun, 21 Dec 2025 20:20:50 -0800 Subject: [PATCH] [clang][bytecode] Fix incorrect handling of arithmetic on string literals Fixes #173175. The fast path for string literals fails to consider the offset of the pointer into an array of chars, this change simply adds the required checks and bounds corrections prior to calling strnlen. --- clang/lib/AST/ByteCode/Context.cpp | 6 +- ...e-interpreter-constant-string-evaluation.c | 160 ++++++++++++++++++ 2 files changed, 164 insertions(+), 2 deletions(-) create mode 100644 clang/test/Sema/bytecode-interpreter-constant-string-evaluation.c diff --git a/clang/lib/AST/ByteCode/Context.cpp b/clang/lib/AST/ByteCode/Context.cpp index 74ec986e49ca7..a64c1e3756062 100644 --- a/clang/lib/AST/ByteCode/Context.cpp +++ b/clang/lib/AST/ByteCode/Context.cpp @@ -294,12 +294,14 @@ bool Context::evaluateStrlen(State &Parent, const Expr *E, uint64_t &Result) { if (!FieldDesc->isPrimitiveArray()) return false; - if (Ptr.isDummy() || Ptr.isUnknownSizeArray()) + if (Ptr.isDummy() || Ptr.isUnknownSizeArray() || Ptr.isPastEnd()) return false; unsigned N = Ptr.getNumElems(); if (Ptr.elemSize() == 1) { - Result = strnlen(reinterpret_cast<const char *>(Ptr.getRawAddress()), N); + unsigned Size = N - Ptr.getIndex(); + Result = + strnlen(reinterpret_cast<const char *>(Ptr.getRawAddress()), Size); return Result != N; } diff --git a/clang/test/Sema/bytecode-interpreter-constant-string-evaluation.c b/clang/test/Sema/bytecode-interpreter-constant-string-evaluation.c new file mode 100644 index 0000000000000..d8b191743698b --- /dev/null +++ b/clang/test/Sema/bytecode-interpreter-constant-string-evaluation.c @@ -0,0 +1,160 @@ +// RUN: %clang_cc1 -x c -std=c2x -fsyntax-only -verify -Wno-string-plus-int -Wno-unused-value %s +// RUN: %clang_cc1 -x c -std=c2x -fsyntax-only -verify -Wno-string-plus-int -Wno-unused-value %s -fexperimental-new-constant-interpreter +// RUN: %clang_cc1 -x c++ -std=c++23 -fsyntax-only -verify -Wno-string-plus-int -Wno-unused-value %s +// RUN: %clang_cc1 -x c++ -std=c++23 -fsyntax-only -verify -Wno-string-plus-int -Wno-unused-value %s -fexperimental-new-constant-interpreter + +void test(char* c) { + __builtin_strcat(c, "42" + 0); + __builtin_strcat(c, "42" + 1); + __builtin_strcat(c, "42" + 2); + __builtin_strcat(c, "42" + 3); + __builtin_strcat(c, "42" + 4); + char buffer[10]; + __builtin_sprintf(buffer, "%%d%d%d"+0, 1); + // expected-warning@-1 {{more '%' conversions than data arguments}} + __builtin_sprintf(buffer, "%%d%d%d"+1, 1); + // expected-warning@-1 {{more '%' conversions than data arguments}} + __builtin_sprintf(buffer, "%%d%d%d"+2, 1); + // expected-warning@-1 {{more '%' conversions than data arguments}} + __builtin_sprintf(buffer, "%%d%d%d"+3, 1); + // expected-warning@-1 {{more '%' conversions than data arguments}} + __builtin_sprintf(buffer, "%%d%d%d"+4, 1); + __builtin_sprintf(buffer, "%%d%d%d"+5, 1); + __builtin_sprintf(buffer, "%%d%d%d"+6, 1); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+7, 1); + // expected-warning@-1 {{format string is empty}} + __builtin_sprintf(buffer, "%%d%d%d"+8, 1); + // TODO: we should probably warning about the format string being out of bounds + + __builtin_sprintf(buffer, "%%d%d%d"+0, 1, 2); + __builtin_sprintf(buffer, "%%d%d%d"+1, 1, 2); + // expected-warning@-1 {{more '%' conversions than data arguments}} + __builtin_sprintf(buffer, "%%d%d%d"+2, 1, 2); + __builtin_sprintf(buffer, "%%d%d%d"+3, 1, 2); + __builtin_sprintf(buffer, "%%d%d%d"+4, 1, 2); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+5, 1, 2); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+6, 1, 2); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+7, 1, 2); + // expected-warning@-1 {{format string is empty}} + __builtin_sprintf(buffer, "%%d%d%d"+8, 1, 2); + __builtin_sprintf(buffer, "%%d%d%d"+9, 1, 2); + + __builtin_sprintf(buffer, "%%d%d%d"+0, 1, 2, 3); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+1, 1, 2, 3); + __builtin_sprintf(buffer, "%%d%d%d"+2, 1, 2, 3); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+3, 1, 2, 3); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+4, 1, 2, 3); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+5, 1, 2, 3); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+6, 1, 2, 3); + // expected-warning@-1 {{data argument not used by format string}} + __builtin_sprintf(buffer, "%%d%d%d"+7, 1, 2, 3); + // expected-warning@-1 {{format string is empty}} + __builtin_sprintf(buffer, "%%d%d%d"+8, 1, 2, 3); + __builtin_sprintf(buffer, "%%d%d%d"+9, 1, 2, 3); + static const char format_string[] = {'%', '%', 'd', '%', 'd', '%', 'd'}; + __builtin_sprintf(buffer, format_string+0, 1); + __builtin_sprintf(buffer, format_string+1, 1); + __builtin_sprintf(buffer, format_string+2, 1); + __builtin_sprintf(buffer, format_string+3, 1); + __builtin_sprintf(buffer, format_string+4, 1); + __builtin_sprintf(buffer, format_string+5, 1); + __builtin_sprintf(buffer, format_string+6, 1); + __builtin_sprintf(buffer, format_string+7, 1); + #ifdef __cplusplus + static constexpr char ce_format_string[] = {'%', '%', 'd', '%', 'd', '%', 'd'}; + __builtin_sprintf(buffer, ce_format_string+0, 1); + __builtin_sprintf(buffer, ce_format_string+1, 1); + __builtin_sprintf(buffer, ce_format_string+2, 1); + __builtin_sprintf(buffer, ce_format_string+3, 1); + __builtin_sprintf(buffer, ce_format_string+4, 1); + __builtin_sprintf(buffer, ce_format_string+5, 1); + __builtin_sprintf(buffer, ce_format_string+6, 1); + __builtin_sprintf(buffer, ce_format_string+7, 1); + #endif +} + +#ifdef __cplusplus +template <class FormatStringSource> bool test_template() { + char buffer[10]; + __builtin_sprintf(buffer, FormatStringSource::format(0), 1); // #template_test1 + __builtin_sprintf(buffer, FormatStringSource::format(1), 1); // #template_test2 + __builtin_sprintf(buffer, FormatStringSource::format(2), 1); // #template_test3 + __builtin_sprintf(buffer, FormatStringSource::format(3), 1); // #template_test4 + __builtin_sprintf(buffer, FormatStringSource::format(4), 1); // #template_test5 + __builtin_sprintf(buffer, FormatStringSource::format(5), 1); // #template_test6 + __builtin_sprintf(buffer, FormatStringSource::format(6), 1); // #template_test7 + __builtin_sprintf(buffer, FormatStringSource::format(7), 1); // #template_test8 + __builtin_sprintf(buffer, FormatStringSource::format(8), 1); // #template_test9 + return true; +} + +struct LiteralFormatStr { + static consteval const char *format(int N) { + return "%%d%d%d" + N; // #LiteralFormatStrLiteral + } +}; + +struct ConstLiteralFormatStr { + static constexpr const char *formatStr = "%%d%d%d"; // #ConstLiteralFormatStrLiteral + static consteval const char *format(int N) { + return formatStr + N; + } +}; + +struct NullTerminatedArrayFormatStr { + static constexpr char formatStr[] = {'%', '%', 'd', '%', 'd', '%', 'd', 0}; + static consteval const char *format(int N) { + return formatStr + N; + } +}; + +struct NoNullTerminatedArrayFormatStr { + static constexpr char formatStr[] = {'%', '%', 'd', '%', 'd', '%', 'd'}; + static consteval const char *format(int N) { + return formatStr + N; // #NoNullTerminatedArrayFormatStr_format + } +}; + +void test_templates() { + test_template<LiteralFormatStr>(); + // expected-note@-1 {{in instantiation of function template specialization 'test_template<LiteralFormatStr>' requested here}} + // expected-warning@#template_test1 {{more '%' conversions than data arguments}} + // expected-warning@#template_test2 {{more '%' conversions than data arguments}} + // expected-warning@#template_test3 {{more '%' conversions than data arguments}} + // expected-warning@#template_test4 {{more '%' conversions than data arguments}} + // expected-warning@#template_test5 {{more '%' conversions than data arguments}} + // expected-warning@#template_test6 {{more '%' conversions than data arguments}} + // expected-warning@#template_test7 {{more '%' conversions than data arguments}} + // expected-warning@#template_test8 {{more '%' conversions than data arguments}} + // expected-warning@#template_test9 {{more '%' conversions than data arguments}} + // expected-note@#LiteralFormatStrLiteral 9 {{format string is defined here}} + test_template<ConstLiteralFormatStr>(); + // expected-note@-1 {{in instantiation of function template specialization 'test_template<ConstLiteralFormatStr>' requested here}} + // expected-warning@#template_test1 {{more '%' conversions than data arguments}} + // expected-warning@#template_test2 {{more '%' conversions than data arguments}} + // expected-warning@#template_test3 {{more '%' conversions than data arguments}} + // expected-warning@#template_test4 {{more '%' conversions than data arguments}} + // expected-warning@#template_test5 {{more '%' conversions than data arguments}} + // expected-warning@#template_test6 {{more '%' conversions than data arguments}} + // expected-warning@#template_test7 {{more '%' conversions than data arguments}} + // expected-warning@#template_test8 {{more '%' conversions than data arguments}} + // expected-warning@#template_test9 {{more '%' conversions than data arguments}} + // expected-note@#ConstLiteralFormatStrLiteral 9 {{format string is defined here}} + test_template<NullTerminatedArrayFormatStr>(); + test_template<NoNullTerminatedArrayFormatStr>(); + // expected-note@-1 {{in instantiation of function template specialization 'test_template<NoNullTerminatedArrayFormatStr>' requested here}} + // expected-note@#NoNullTerminatedArrayFormatStr_format {{cannot refer to element 8 of array of 7 elements in a constant expression}} + // expected-error@#template_test9 {{call to consteval function 'NoNullTerminatedArrayFormatStr::format' is not a constant expression}} + // expected-note@#template_test9 {{in call to 'format(8)'}} +} + +#endif _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
