Author: Takuya Shimizu Date: 2023-03-13T12:53:12-04:00 New Revision: 6b48d202ef497f4d512c382fe0db8c5ad3a72faa
URL: https://github.com/llvm/llvm-project/commit/6b48d202ef497f4d512c382fe0db8c5ad3a72faa DIFF: https://github.com/llvm/llvm-project/commit/6b48d202ef497f4d512c382fe0db8c5ad3a72faa.diff LOG: [clang][AST] Improve diagnostic for `nullptr` constexpr function pointer call This patch improves diagnostic for clang constexpr evaluator by adding a check for nullptr in function pointer call evaluations. ex. ``` constexpr int foo(int (*bla)(void)) { return bla(); } static_assert(foo(nullptr) == 1); ``` BEFORE this patch, clang generates the following diagnostic for the code above: ``` <source>:5:15: error: static assertion expression is not an integral constant expression static_assert(foo(nullptr) == 1); ^~~~~~~~~~~~~~~~~ <source>:2:10: note: subexpression not valid in a constant expression return bla(); ^ <source>:5:15: note: in call to 'foo(nullptr)' static_assert(foo(nullptr) == 1); ^ 1 error generated. ``` AFTER this patch, subexpression not valid in a constant expression note is replaced with 'bla' evaluates to a null function pointer. Fixes https://github.com/llvm/llvm-project/issues/59872 Differential Revision: https://reviews.llvm.org/D145793 Added: Modified: clang/docs/ReleaseNotes.rst clang/include/clang/Basic/DiagnosticASTKinds.td clang/lib/AST/ExprConstant.cpp clang/test/SemaCXX/constant-expression-cxx11.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 440fd04274777..a8c6f2f733d78 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -165,6 +165,8 @@ Improvements to Clang's diagnostics - Diagnostics relating to macros on the command line of a preprocessed assembly file are now reported as coming from the file ``<command line>`` instead of ``<built-in>``. +- Clang constexpr evaluator now provides a more concise diagnostic when calling + function pointer that is known to be null. Bug Fixes in This Version ------------------------- diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td index 28120d13fd9e7..c283ee842e730 100644 --- a/clang/include/clang/Basic/DiagnosticASTKinds.td +++ b/clang/include/clang/Basic/DiagnosticASTKinds.td @@ -127,6 +127,8 @@ def note_constexpr_null_subobject : Note< "access array element of|perform pointer arithmetic on|" "access real component of|" "access imaginary component of}0 null pointer">; +def note_constexpr_null_callee : Note< + "'%0' evaluates to a null function pointer">; def note_constexpr_function_param_value_unknown : Note< "function parameter %0 with unknown value cannot be used in a constant " "expression">; diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp index 26c23423b858f..fbe92d054d6bc 100644 --- a/clang/lib/AST/ExprConstant.cpp +++ b/clang/lib/AST/ExprConstant.cpp @@ -7668,6 +7668,11 @@ class ExprEvaluatorBase if (!CalleeLV.getLValueOffset().isZero()) return Error(Callee); + if (CalleeLV.isNullPointer()) { + Info.FFDiag(Callee, diag::note_constexpr_null_callee) + << const_cast<Expr *>(Callee); + return false; + } FD = dyn_cast_or_null<FunctionDecl>( CalleeLV.getLValueBase().dyn_cast<const ValueDecl *>()); if (!FD) diff --git a/clang/test/SemaCXX/constant-expression-cxx11.cpp b/clang/test/SemaCXX/constant-expression-cxx11.cpp index fea45d56f0fd3..5e7a80c81eaee 100644 --- a/clang/test/SemaCXX/constant-expression-cxx11.cpp +++ b/clang/test/SemaCXX/constant-expression-cxx11.cpp @@ -279,7 +279,7 @@ namespace FunctionPointers { constexpr auto Select(int n) -> int (*)(int) { return n == 2 ? &Double : n == 3 ? &Triple : n == 4 ? &Quadruple : 0; } - constexpr int Apply(int (*F)(int), int n) { return F(n); } // expected-note {{subexpression}} + constexpr int Apply(int (*F)(int), int n) { return F(n); } // expected-note {{'F' evaluates to a null function pointer}} static_assert(1 + Apply(Select(4), 5) + Apply(Select(3), 7) == 42, ""); _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
