[clang] Add clang warning if fp exception functions are called without appropriate flags/pragmas (PR #199009)
Marcos Ramirez Joos via cfe-commits
cfe-commits at lists.llvm.org
Wed Jul 1 06:55:42 PDT 2026
https://github.com/maarcosrmz updated https://github.com/llvm/llvm-project/pull/199009
>From 0de126da44f519f1d8f943595f6274e10d40bf69 Mon Sep 17 00:00:00 2001
From: Marcos Ramirez Joos <mramirezjoos.oss at proton.me>
Date: Sun, 17 May 2026 22:43:47 +0200
Subject: [PATCH 1/5] Add clang warning if fp exception functions are called
without appropriate flags/pragmas (#187860)
Fixes https://github.com/llvm/llvm-project/issues/128239
The implementation adds warnings for floating-point exception function
calls (fenv.h) made without enabling floating-point exception behavior
via `-ffp-exception-behavior=maytrap/strict` or `#pragma STDC
FENV_ACCESS ON`. To support recognition of all fenv.h builtins,
`fexcept_t` and `fenv_t` were added as builtin types.
---
clang/include/clang/AST/ASTContext.h | 35 +++++++++-
clang/include/clang/Basic/BuiltinHeaders.def | 1 +
clang/include/clang/Basic/Builtins.td | 55 +++++++++++++++
.../clang/Basic/DiagnosticSemaKinds.td | 5 ++
clang/include/clang/Basic/TokenKinds.def | 2 +
clang/include/clang/Sema/Sema.h | 4 ++
.../include/clang/Serialization/ASTBitCodes.h | 8 ++-
clang/lib/AST/ASTContext.cpp | 19 ++++++
clang/lib/Sema/SemaChecking.cpp | 18 +++++
clang/lib/Sema/SemaDecl.cpp | 8 +++
clang/lib/Serialization/ASTReader.cpp | 36 ++++++++++
clang/lib/Serialization/ASTWriter.cpp | 2 +
clang/test/PCH/builtins-fenv.c | 25 +++++++
clang/test/PCH/builtins-fenv.h | 18 +++++
clang/test/Sema/builtin-fenv.c | 51 ++++++++++++++
clang/test/Sema/fenv-access-implicit.c | 35 ++++++++++
clang/test/Sema/fenv-access-unevaluated.cpp | 31 +++++++++
clang/test/Sema/fenv-access.c | 68 +++++++++++++++++++
clang/utils/TableGen/ClangBuiltinsEmitter.cpp | 2 +
19 files changed, 421 insertions(+), 2 deletions(-)
create mode 100644 clang/test/PCH/builtins-fenv.c
create mode 100644 clang/test/PCH/builtins-fenv.h
create mode 100644 clang/test/Sema/builtin-fenv.c
create mode 100644 clang/test/Sema/fenv-access-implicit.c
create mode 100644 clang/test/Sema/fenv-access-unevaluated.cpp
create mode 100644 clang/test/Sema/fenv-access.c
diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index a4ed852d36442..763e4df87f08a 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -495,6 +495,12 @@ class ASTContext : public RefCountedBase<ASTContext> {
/// The type for the C ucontext_t type.
TypeDecl *ucontext_tDecl = nullptr;
+ /// The type for the C fexcept_t type.
+ TypeDecl *fexcept_tDecl = nullptr;
+
+ /// The type for the C fenv_t type.
+ TypeDecl *fenv_tDecl = nullptr;
+
/// Type for the Block descriptor for Blocks CodeGen.
///
/// Since this is only used for generation of debug info, it is not
@@ -2360,6 +2366,30 @@ class ASTContext : public RefCountedBase<ASTContext> {
return QualType();
}
+ /// Set the type for the C fexcept_t type.
+ void setfexcept_tDecl(TypeDecl *fexcept_tDecl) {
+ this->fexcept_tDecl = fexcept_tDecl;
+ }
+
+ /// Retrieve the C fexcept_t type.
+ QualType getfexcept_tType() const {
+ if (fexcept_tDecl)
+ return getTypeDeclType(ElaboratedTypeKeyword::None,
+ /*Qualifier=*/std::nullopt, fexcept_tDecl);
+ return QualType();
+ }
+
+ /// Set the type for the C fenv_t type.
+ void setfenv_tDecl(TypeDecl *fenv_tDecl) { this->fenv_tDecl = fenv_tDecl; }
+
+ /// Retrieve the C fenv_t type.
+ QualType getfenv_tType() const {
+ if (fenv_tDecl)
+ return getTypeDeclType(ElaboratedTypeKeyword::None,
+ /*Qualifier=*/std::nullopt, fenv_tDecl);
+ return QualType();
+ }
+
/// The result type of logical operations, '<', '>', '!=', etc.
CanQualType getLogicalOperationType() const {
return getLangOpts().CPlusPlus ? BoolTy : IntTy;
@@ -2640,7 +2670,10 @@ class ASTContext : public RefCountedBase<ASTContext> {
GE_Missing_setjmp,
/// Missing a type from <ucontext.h>
- GE_Missing_ucontext
+ GE_Missing_ucontext,
+
+ /// Missing a type from <fenv.h>
+ GE_Missing_fenv
};
QualType DecodeTypeStr(const char *&Str, const ASTContext &Context,
diff --git a/clang/include/clang/Basic/BuiltinHeaders.def b/clang/include/clang/Basic/BuiltinHeaders.def
index b18e470a8bd25..d47803aafafa7 100644
--- a/clang/include/clang/Basic/BuiltinHeaders.def
+++ b/clang/include/clang/Basic/BuiltinHeaders.def
@@ -17,6 +17,7 @@ HEADER(BLOCKS_H, "Blocks.h")
HEADER(COMPLEX_H, "complex.h")
HEADER(CTYPE_H, "ctype.h")
HEADER(EMMINTRIN_H, "emmintrin.h")
+HEADER(FENV_H, "fenv.h")
HEADER(FOUNDATION_NSOBJCRUNTIME_H, "Foundation/NSObjCRuntime.h")
HEADER(IMMINTRIN_H, "immintrin.h")
HEADER(INTRIN_H, "intrin.h")
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index 506f47fb597af..3f057b5f1cf68 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -4696,6 +4696,61 @@ def BlockObjectDispose : LibBuiltin<"blocks.h"> {
}
// FIXME: Also declare NSConcreteGlobalBlock and NSConcreteStackBlock.
+def FeClearExcept : LibBuiltin<"fenv.h"> {
+ let Spellings = ["feclearexcept"];
+ let Prototype = "int(int)";
+}
+
+def FeGetExceptFlag : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fegetexceptflag"];
+ let Prototype = "int(fexcept_t*, int)";
+}
+
+def FeRaiseExcept : LibBuiltin<"fenv.h"> {
+ let Spellings = ["feraiseexcept"];
+ let Prototype = "int(int)";
+}
+
+def FeSetExceptFlag : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fesetexceptflag"];
+ let Prototype = "int(fexcept_t const*, int)";
+}
+
+def FeTestExcept : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fetestexcept"];
+ let Prototype = "int(int)";
+}
+
+def FeGetRound : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fegetround"];
+ let Prototype = "int()";
+}
+
+def FeSetRound : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fesetround"];
+ let Prototype = "int(int)";
+}
+
+def FeGetEnv : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fegetenv"];
+ let Prototype = "int(fenv_t*)";
+}
+
+def FeHoldExcept : LibBuiltin<"fenv.h"> {
+ let Spellings = ["feholdexcept"];
+ let Prototype = "int(fenv_t*)";
+}
+
+def FeSetEnv : LibBuiltin<"fenv.h"> {
+ let Spellings = ["fesetenv"];
+ let Prototype = "int(fenv_t const*)";
+}
+
+def FeUpdateEnv : LibBuiltin<"fenv.h"> {
+ let Spellings = ["feupdateenv"];
+ let Prototype = "int(fenv_t const*)";
+}
+
def __Addressof : LangBuiltin<"CXX_LANG"> {
let Spellings = ["__addressof"];
let Attributes = [FunctionWithoutBuiltinPrefix, NoThrow, Const,
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 86b765fdf1fab..fb149ebcdd8ec 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1053,6 +1053,11 @@ def err_ptrauth_indirect_goto_addrlabel_arithmetic : Error<
"%select{subtraction|addition}0 of address-of-label expressions is not "
"supported with ptrauth indirect gotos">;
+def warn_fe_access_without_fenv_access : Warning<
+ "'%0' used without enabling floating-point exception behavior; use 'pragma STDC "
+ "FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'">,
+ InGroup<DiagGroup<"fenv-access">>;
+
// __ptrauth qualifier
def err_ptrauth_qualifier_invalid : Error<
"%select{return type|parameter type|property}1 may not be qualified with "
diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
index f07d8ebb75035..4bd21b4112580 100644
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -877,6 +877,8 @@ NOTABLE_IDENTIFIER(FILE)
NOTABLE_IDENTIFIER(jmp_buf)
NOTABLE_IDENTIFIER(sigjmp_buf)
NOTABLE_IDENTIFIER(ucontext_t)
+NOTABLE_IDENTIFIER(fexcept_t)
+NOTABLE_IDENTIFIER(fenv_t)
NOTABLE_IDENTIFIER(float_t)
NOTABLE_IDENTIFIER(double_t)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index ebb775ffbb758..38e09dae1e9d5 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -8259,6 +8259,10 @@ class Sema final : public SemaBase {
return currentEvaluationContext().isUnevaluated();
}
+ bool isPotentiallyEvaluatedContext() const {
+ return currentEvaluationContext().isPotentiallyEvaluated();
+ }
+
bool isImmediateFunctionContext() const {
return currentEvaluationContext().isImmediateFunctionContext();
}
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index 279380de2f7fe..d323bcc79bab8 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -1217,7 +1217,13 @@ enum SpecialTypeIDs {
SPECIAL_TYPE_OBJC_SEL_REDEFINITION = 6,
/// C ucontext_t typedef type
- SPECIAL_TYPE_UCONTEXT_T = 7
+ SPECIAL_TYPE_UCONTEXT_T = 7,
+
+ /// C fexcept_t typedef type
+ SPECIAL_TYPE_FEXCEPT_T = 8,
+
+ /// C fenv_t typedef type
+ SPECIAL_TYPE_FENV_T = 9
};
/// The number of special type IDs.
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index abf0cd5e18c2b..a700143d1ba47 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -12921,6 +12921,25 @@ static QualType DecodeTypeFromStr(const char *&Str, const ASTContext &Context,
case 'm':
Type = Context.MFloat8Ty;
break;
+ case 'T':
+ switch (*Str++) {
+ case 'x': {
+ Type = Context.getfexcept_tType();
+ break;
+ }
+ case 'e': {
+ Type = Context.getfenv_tType();
+ break;
+ }
+ default: {
+ llvm_unreachable("Unexpected target builtin type");
+ }
+ }
+ if (Type.isNull()) {
+ Error = ASTContext::GE_Missing_fenv;
+ return {};
+ }
+ break;
}
// If there are modifiers and if we're allowed to parse them, go for it.
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 01b1f4c26f017..a27b6e073713a 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -4146,6 +4146,24 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
if (BuiltinCountedByRef(TheCall))
return ExprError();
break;
+
+ case Builtin::BIfeclearexcept:
+ case Builtin::BIfegetexceptflag:
+ case Builtin::BIferaiseexcept:
+ case Builtin::BIfesetexceptflag:
+ case Builtin::BIfetestexcept:
+ case Builtin::BIfegetround:
+ case Builtin::BIfesetround:
+ case Builtin::BIfegetenv:
+ case Builtin::BIfeholdexcept:
+ case Builtin::BIfesetenv:
+ case Builtin::BIfeupdateenv:
+ if (TheCall->getFPFeaturesInEffect(getLangOpts()).getExceptionMode() ==
+ LangOptions::FPE_Ignore &&
+ isPotentiallyEvaluatedContext()) {
+ Diag(TheCall->getBeginLoc(), diag::warn_fe_access_without_fenv_access)
+ << FDecl->getName() << TheCall->getSourceRange();
+ }
}
if (getLangOpts().HLSL && HLSL().CheckBuiltinFunctionCall(BuiltinID, TheCall))
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index f6d1d7a7877c7..1edce35b03697 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2398,6 +2398,8 @@ static StringRef getHeaderName(Builtin::Context &BuiltinInfo, unsigned ID,
return "setjmp.h";
case ASTContext::GE_Missing_ucontext:
return "ucontext.h";
+ case ASTContext::GE_Missing_fenv:
+ return "fenv.h";
}
llvm_unreachable("unhandled error kind");
}
@@ -7020,6 +7022,12 @@ Sema::ActOnTypedefNameDecl(Scope *S, DeclContext *DC, TypedefNameDecl *NewTD,
case tok::NotableIdentifierKind::ucontext_t:
Context.setucontext_tDecl(NewTD);
break;
+ case tok::NotableIdentifierKind::fexcept_t:
+ Context.setfexcept_tDecl(NewTD);
+ break;
+ case tok::NotableIdentifierKind::fenv_t:
+ Context.setfenv_tDecl(NewTD);
+ break;
case tok::NotableIdentifierKind::float_t:
case tok::NotableIdentifierKind::double_t:
NewTD->addAttr(AvailableOnlyInDefaultEvalMethodAttr::Create(Context));
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index b01b18fe3e0ec..a5d426a43cd08 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -5755,6 +5755,42 @@ void ASTReader::InitializeContext() {
}
}
}
+
+ if (TypeID Fexcept_t = SpecialTypes[SPECIAL_TYPE_FEXCEPT_T]) {
+ QualType Fexcept_tType = GetType(Fexcept_t);
+ if (Fexcept_tType.isNull()) {
+ Error("fexcept_t type is NULL");
+ return;
+ }
+
+ if (!Context.fexcept_tDecl) {
+ if (const TypedefType *Typedef = Fexcept_tType->getAs<TypedefType>())
+ Context.setfexcept_tDecl(Typedef->getDecl());
+ else {
+ const TagType *Tag = Fexcept_tType->getAs<TagType>();
+ assert(Tag && "Invalid fexcept_t type in AST file");
+ Context.setfexcept_tDecl(Tag->getDecl());
+ }
+ }
+ }
+
+ if (TypeID Fenv_t = SpecialTypes[SPECIAL_TYPE_FENV_T]) {
+ QualType Fenv_tType = GetType(Fenv_t);
+ if (Fenv_tType.isNull()) {
+ Error("fenv_t type is NULL");
+ return;
+ }
+
+ if (!Context.fenv_tDecl) {
+ if (const TypedefType *Typedef = Fenv_tType->getAs<TypedefType>())
+ Context.setfenv_tDecl(Typedef->getDecl());
+ else {
+ const TagType *Tag = Fenv_tType->getAs<TagType>();
+ assert(Tag && "Invalid fenv_t type in AST file");
+ Context.setfenv_tDecl(Tag->getDecl());
+ }
+ }
+ }
}
ReadPragmaDiagnosticMappings(Context.getDiagnostics());
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index ecf935e3b3548..2ba75b8184ce9 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6137,6 +6137,8 @@ ASTFileSignature ASTWriter::WriteASTCore(Sema *SemaPtr, StringRef isysroot,
AddTypeRef(Context, Context.ObjCClassRedefinitionType, SpecialTypes);
AddTypeRef(Context, Context.ObjCSelRedefinitionType, SpecialTypes);
AddTypeRef(Context, Context.getucontext_tType(), SpecialTypes);
+ AddTypeRef(Context, Context.getfexcept_tType(), SpecialTypes);
+ AddTypeRef(Context, Context.getfenv_tType(), SpecialTypes);
}
if (SemaPtr)
diff --git a/clang/test/PCH/builtins-fenv.c b/clang/test/PCH/builtins-fenv.c
new file mode 100644
index 0000000000000..72bcf4a134730
--- /dev/null
+++ b/clang/test/PCH/builtins-fenv.c
@@ -0,0 +1,25 @@
+// Test this without pch.
+// RUN: %clang_cc1 -include %S/builtins-fenv.h -fsyntax-only -verify %s
+
+// Test with pch.
+// RUN: %clang_cc1 -emit-pch -o %t %S/builtins-fenv.h
+// RUN: %clang_cc1 -include-pch %t -fsyntax-only -verify %s
+
+// expected-no-diagnostics
+fexcept_t *flagp = 0;
+fenv_t *envp = 0;
+
+void f(void) {
+ #pragma STDC FENV_ACCESS ON
+ feclearexcept(FE_INVALID);
+ fegetexceptflag(flagp, FE_INVALID);
+ feraiseexcept(FE_INVALID);
+ fesetexceptflag(flagp, FE_INVALID);
+ fetestexcept(FE_INVALID);
+ fegetround();
+ fesetround(0);
+ fegetenv(envp);
+ feholdexcept(envp);
+ fesetenv(envp);
+ feupdateenv(envp);
+}
diff --git a/clang/test/PCH/builtins-fenv.h b/clang/test/PCH/builtins-fenv.h
new file mode 100644
index 0000000000000..8397c270df58e
--- /dev/null
+++ b/clang/test/PCH/builtins-fenv.h
@@ -0,0 +1,18 @@
+// Header for PCH test builtins-fenv.c
+
+#define FE_INVALID 1
+
+typedef struct {} fenv_t;
+typedef unsigned short int fexcept_t;
+
+int feclearexcept(int excepts);
+int fegetexceptflag(fexcept_t *flagp, int excepts);
+int feraiseexcept(int excepts);
+int fesetexceptflag(const fexcept_t *flagp, int excepts);
+int fetestexcept(int excepts);
+int fegetround(void);
+int fesetround(int rounding_mode);
+int fegetenv(fenv_t *envp);
+int feholdexcept(fenv_t *envp);
+int fesetenv(const fenv_t *envp);
+int feupdateenv(const fenv_t *envp);
diff --git a/clang/test/Sema/builtin-fenv.c b/clang/test/Sema/builtin-fenv.c
new file mode 100644
index 0000000000000..db8a5334d1073
--- /dev/null
+++ b/clang/test/Sema/builtin-fenv.c
@@ -0,0 +1,51 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -verify=c,expected -DWRONG_FEXCEPT_T %s -ast-dump | FileCheck %s --check-prefixes=CHECK1,CHECK2
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -verify=c,expected -DRIGHT_FEXCEPT_T %s -ast-dump | FileCheck %s --check-prefixes=CHECK1,CHECK2
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -verify=c,expected -DONLY_FEXCEPT_T %s -ast-dump | FileCheck %s --check-prefixes=CHECK1,CHECK2
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -verify=c,expected -DNO_FEGETEXCEPTFLAG %s -ast-dump 2>&1 | FileCheck %s --check-prefixes=CHECK1
+
+// tests inspired by clang/test/Sema/builtin-setjmp.c
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if WRONG_FEXCEPT_T
+typedef unsigned short int fexcept_t;
+extern int fegetexceptflag(int, int); // c-warning {{incompatible redeclaration of library function 'fegetexceptflag'}}
+ // c-note at -1 {{'fegetexceptflag' is a builtin with type 'int (fexcept_t *, int)' (aka 'int (unsigned short *, int)')}}
+#elif RIGHT_FEXCEPT_T
+// c-no-diagnostics
+typedef unsigned short int fexcept_t;
+extern int fegetexceptflag(unsigned short int *, int); // OK, right type.
+#elif ONLY_FEXCEPT_T
+typedef long *fexcept_t;
+#endif
+
+void use(void) {
+ #pragma STDC FENV_ACCESS ON
+ fegetexceptflag(0, 0);
+ #if NO_FEGETEXCEPTFLAG
+ // cxx-error at -2 {{undeclared identifier 'fegetexceptflag'}}
+ // c-error at -3 {{call to undeclared function 'fegetexceptflag'; ISO C99 and later do not support implicit function declarations}}
+ // c-warning at -4 {{declaration of built-in function 'fegetexceptflag' requires inclusion of the header <fenv.h>}}
+ #elif ONLY_FEXCEPT_T
+ // cxx-error at -6 {{undeclared identifier 'fegetexceptflag'}}
+ // c-error at -7 {{call to undeclared library function 'fegetexceptflag' with type 'int (fexcept_t *, int)' (aka 'int (long **, int)'); ISO C99 and later do not support implicit function declarations}}
+ // c-note at -8 {{include the header <fenv.h> or explicitly provide a declaration for 'fegetexceptflag'}}
+ #else
+ // cxx-no-diagnostics
+ #endif
+
+ #ifdef NO_FEGETEXCEPTFLAG
+ // In this case, the regular AST dump doesn't dump the implicit declaration of 'fegetexceptflag'.
+ #pragma clang __debug dump fegetexceptflag
+ #endif
+}
+
+// CHECK1: FunctionDecl {{.*}} used fegetexceptflag
+// CHECK2: BuiltinAttr {{.*}} Implicit
+
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/clang/test/Sema/fenv-access-implicit.c b/clang/test/Sema/fenv-access-implicit.c
new file mode 100644
index 0000000000000..0c4bd6b0eb855
--- /dev/null
+++ b/clang/test/Sema/fenv-access-implicit.c
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -verify -Wfenv-access %s
+
+typedef struct {} fenv_t;
+typedef unsigned short int fexcept_t;
+
+fexcept_t *flagp = 0;
+fenv_t *envp = 0;
+
+#define FE_INVALID 1
+
+void test_fenv_access_undeclared(void) {
+ #pragma STDC FENV_ACCESS ON
+ feclearexcept(FE_INVALID); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'feclearexcept'}} \
+ expected-error {{call to undeclared library function 'feclearexcept' with type 'int (int)'; ISO C99 and later do not support implicit function declarations}}
+ fegetexceptflag(flagp, FE_INVALID); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fegetexceptflag'}} \
+ expected-error {{call to undeclared library function 'fegetexceptflag' with type 'int (fexcept_t *, int)' (aka 'int (unsigned short *, int)'); ISO C99 and later do not support implicit function declarations}}
+ feraiseexcept(FE_INVALID); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'feraiseexcept'}} \
+ expected-error {{call to undeclared library function 'feraiseexcept' with type 'int (int)'; ISO C99 and later do not support implicit function declarations}}
+ fesetexceptflag(flagp, FE_INVALID); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fesetexceptflag'}} \
+ expected-error {{call to undeclared library function 'fesetexceptflag' with type 'int (const fexcept_t *, int)' (aka 'int (const unsigned short *, int)'); ISO C99 and later do not support implicit function declarations}}
+ fetestexcept(FE_INVALID); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fetestexcept'}} \
+ expected-error {{call to undeclared library function 'fetestexcept' with type 'int (int)'; ISO C99 and later do not support implicit function declarations}}
+ fegetround(); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fegetround'}} \
+ expected-error {{call to undeclared library function 'fegetround' with type 'int (void)'; ISO C99 and later do not support implicit function declarations}}
+ fesetround(0); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fesetround'}} \
+ expected-error {{call to undeclared library function 'fesetround' with type 'int (int)'; ISO C99 and later do not support implicit function declarations}}
+ fegetenv(envp); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fegetenv'}} \
+ expected-error {{call to undeclared library function 'fegetenv' with type 'int (fenv_t *)'; ISO C99 and later do not support implicit function declarations}}
+ feholdexcept(envp); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'feholdexcept'}} \
+ expected-error {{call to undeclared library function 'feholdexcept' with type 'int (fenv_t *)'; ISO C99 and later do not support implicit function declarations}}
+ fesetenv(envp); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'fesetenv'}} \
+ expected-error {{call to undeclared library function 'fesetenv' with type 'int (const fenv_t *)'; ISO C99 and later do not support implicit function declarations}}
+ feupdateenv(envp); // expected-note {{include the header <fenv.h> or explicitly provide a declaration for 'feupdateenv'}} \
+ expected-error {{call to undeclared library function 'feupdateenv' with type 'int (const fenv_t *)'; ISO C99 and later do not support implicit function declarations}}
+}
diff --git a/clang/test/Sema/fenv-access-unevaluated.cpp b/clang/test/Sema/fenv-access-unevaluated.cpp
new file mode 100644
index 0000000000000..14752ba3c377e
--- /dev/null
+++ b/clang/test/Sema/fenv-access-unevaluated.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -verify -Wfenv-access %s
+
+typedef struct {} fenv_t;
+typedef unsigned short int fexcept_t;
+
+int feclearexcept(int excepts);
+int fegetexceptflag(fexcept_t *flagp, int excepts);
+int feraiseexcept(int excepts);
+int fesetexceptflag(const fexcept_t *flagp, int excepts);
+int fetestexcept(int excepts);
+int fegetround(void);
+int fesetround(int rounding_mode);
+int fegetenv(fenv_t *envp);
+int feholdexcept(fenv_t *envp);
+int fesetenv(const fenv_t *envp);
+int feupdateenv(const fenv_t *envp);
+
+// expected-no-diagnostics
+void test_fenv_access_unevaluated() {
+ decltype(::feclearexcept) a;
+ decltype(::fegetexceptflag) b;
+ decltype(::feraiseexcept) c;
+ decltype(::fesetexceptflag) d;
+ decltype(::fetestexcept) e;
+ decltype(::fegetround) f;
+ decltype(::fesetround) g;
+ decltype(::fegetenv) h;
+ decltype(::feholdexcept) i;
+ decltype(::fesetenv) j;
+ decltype(::feupdateenv) k;
+}
diff --git a/clang/test/Sema/fenv-access.c b/clang/test/Sema/fenv-access.c
new file mode 100644
index 0000000000000..3a7b95af7ab4c
--- /dev/null
+++ b/clang/test/Sema/fenv-access.c
@@ -0,0 +1,68 @@
+// RUN: %clang_cc1 -verify -Wfenv-access %s
+// RUN: %clang_cc1 -verify -Wfenv-access -ffp-exception-behavior=maytrap -DNO_WARN %s
+// RUN: %clang_cc1 -verify -Wfenv-access -ffp-exception-behavior=strict -DNO_WARN %s
+
+typedef struct {} fenv_t;
+typedef unsigned short int fexcept_t;
+
+int feclearexcept(int excepts);
+int fegetexceptflag(fexcept_t *flagp, int excepts);
+int feraiseexcept(int excepts);
+int fesetexceptflag(const fexcept_t *flagp, int excepts);
+int fetestexcept(int excepts);
+int fegetround(void);
+int fesetround(int rounding_mode);
+int fegetenv(fenv_t *envp);
+int feholdexcept(fenv_t *envp);
+int fesetenv(const fenv_t *envp);
+int feupdateenv(const fenv_t *envp);
+
+#define FE_INVALID 1
+
+fexcept_t *flagp = 0;
+fenv_t *envp = 0;
+
+void test_fenv_access_off(void) {
+#ifdef NO_WARN
+ // expected-no-diagnostics
+ feclearexcept(FE_INVALID);
+ fegetexceptflag(flagp, FE_INVALID);
+ feraiseexcept(FE_INVALID);
+ fesetexceptflag(flagp, FE_INVALID);
+ fetestexcept(FE_INVALID);
+ fegetround();
+ fesetround(0);
+ fegetenv(envp);
+ feholdexcept(envp);
+ fesetenv(envp);
+ feupdateenv(envp);
+#else
+ feclearexcept(FE_INVALID); // expected-warning {{'feclearexcept' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fegetexceptflag(flagp, FE_INVALID); // expected-warning {{'fegetexceptflag' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ feraiseexcept(FE_INVALID); // expected-warning {{'feraiseexcept' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fesetexceptflag(flagp, FE_INVALID); // expected-warning {{'fesetexceptflag' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fetestexcept(FE_INVALID); // expected-warning {{'fetestexcept' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fegetround(); // expected-warning {{'fegetround' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fesetround(0); // expected-warning {{'fesetround' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fegetenv(envp); // expected-warning {{'fegetenv' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ feholdexcept(envp); // expected-warning {{'feholdexcept' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ fesetenv(envp); // expected-warning {{'fesetenv' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+ feupdateenv(envp); // expected-warning {{'feupdateenv' used without enabling floating-point exception behavior; use 'pragma STDC FENV_ACCESS ON' or compile with '-ffp-exception-behavior=maytrap'}}
+#endif
+}
+
+void test_fenv_access_on(void) {
+ #pragma STDC FENV_ACCESS ON
+ fesetround(0);
+ feclearexcept(FE_INVALID);
+ fegetexceptflag(flagp, FE_INVALID);
+ feraiseexcept(FE_INVALID);
+ fesetexceptflag(flagp, FE_INVALID);
+ fetestexcept(FE_INVALID);
+ fegetround();
+ fesetround(0);
+ fegetenv(envp);
+ feholdexcept(envp);
+ fesetenv(envp);
+ feupdateenv(envp);
+}
diff --git a/clang/utils/TableGen/ClangBuiltinsEmitter.cpp b/clang/utils/TableGen/ClangBuiltinsEmitter.cpp
index 4f7f437bcf73c..4ed98ddd3808a 100644
--- a/clang/utils/TableGen/ClangBuiltinsEmitter.cpp
+++ b/clang/utils/TableGen/ClangBuiltinsEmitter.cpp
@@ -380,6 +380,8 @@ class PrototypeParser {
.Case("uint64_t", "UWi")
.Case("void", "v")
.Case("wchar_t", "w")
+ .Case("fexcept_t", "Tx")
+ .Case("fenv_t", "Te")
.Case("...", ".")
.Default("error");
if (ReturnTypeVal == "error")
>From 52a93ad2399fa5082c9b70f57f5ba8b0bc9aed81 Mon Sep 17 00:00:00 2001
From: Marcos Ramirez Joos <mramirezjoos.oss at proton.me>
Date: Thu, 21 May 2026 15:10:06 +0200
Subject: [PATCH 2/5] Added check for strict FP support before warning
---
clang/lib/Sema/SemaChecking.cpp | 4 +++-
clang/test/Sema/fenv-access.c | 3 +++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index a27b6e073713a..e7e3f79fa2192 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -4160,7 +4160,9 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
case Builtin::BIfeupdateenv:
if (TheCall->getFPFeaturesInEffect(getLangOpts()).getExceptionMode() ==
LangOptions::FPE_Ignore &&
- isPotentiallyEvaluatedContext()) {
+ isPotentiallyEvaluatedContext() &&
+ (getASTContext().getTargetInfo().hasStrictFP() ||
+ getLangOpts().ExpStrictFP)) {
Diag(TheCall->getBeginLoc(), diag::warn_fe_access_without_fenv_access)
<< FDecl->getName() << TheCall->getSourceRange();
}
diff --git a/clang/test/Sema/fenv-access.c b/clang/test/Sema/fenv-access.c
index 3a7b95af7ab4c..50a4d9fd16aa2 100644
--- a/clang/test/Sema/fenv-access.c
+++ b/clang/test/Sema/fenv-access.c
@@ -1,6 +1,7 @@
// RUN: %clang_cc1 -verify -Wfenv-access %s
// RUN: %clang_cc1 -verify -Wfenv-access -ffp-exception-behavior=maytrap -DNO_WARN %s
// RUN: %clang_cc1 -verify -Wfenv-access -ffp-exception-behavior=strict -DNO_WARN %s
+// RUN: %clang_cc1 -verify -Wfenv-access -triple armv7-linux-gnueabihf -DNO_WARN -DUNSUPPORTED %s
typedef struct {} fenv_t;
typedef unsigned short int fexcept_t;
@@ -52,7 +53,9 @@ void test_fenv_access_off(void) {
}
void test_fenv_access_on(void) {
+#ifndef UNSUPPORTED
#pragma STDC FENV_ACCESS ON
+#endif
fesetround(0);
feclearexcept(FE_INVALID);
fegetexceptflag(flagp, FE_INVALID);
>From 45ce4ec0ea9a010b647413831afa93d9f989e8db Mon Sep 17 00:00:00 2001
From: Marcos Ramirez Joos <mramirezjoos.oss at proton.me>
Date: Thu, 21 May 2026 15:19:25 +0200
Subject: [PATCH 3/5] Removed redundant extern "C" {} block in builtin-fenv.c
---
clang/test/Sema/builtin-fenv.c | 9 ---------
1 file changed, 9 deletions(-)
diff --git a/clang/test/Sema/builtin-fenv.c b/clang/test/Sema/builtin-fenv.c
index db8a5334d1073..c9b2306326326 100644
--- a/clang/test/Sema/builtin-fenv.c
+++ b/clang/test/Sema/builtin-fenv.c
@@ -5,10 +5,6 @@
// tests inspired by clang/test/Sema/builtin-setjmp.c
-#ifdef __cplusplus
-extern "C" {
-#endif
-
#if WRONG_FEXCEPT_T
typedef unsigned short int fexcept_t;
extern int fegetexceptflag(int, int); // c-warning {{incompatible redeclaration of library function 'fegetexceptflag'}}
@@ -44,8 +40,3 @@ void use(void) {
// CHECK1: FunctionDecl {{.*}} used fegetexceptflag
// CHECK2: BuiltinAttr {{.*}} Implicit
-
-
-#ifdef __cplusplus
-}
-#endif
>From beefde83463054c61e4b45099382a2dae081ccf6 Mon Sep 17 00:00:00 2001
From: Marcos Ramirez Joos <mramirezjoos.oss at proton.me>
Date: Wed, 1 Jul 2026 12:27:00 +0200
Subject: [PATCH 4/5] Added release notes to new clang/docs/ReleaseNotes.md
file
---
clang/docs/ReleaseNotes.md | 3 +++
1 file changed, 3 insertions(+)
diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index e4f992f6e0f08..9fd529e874fa5 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -679,6 +679,9 @@ latest release, please see the [Clang Web Site](https://clang.llvm.org) or the
by the kernel, so setting them is almost always a typo (matching the
bionic libc `diagnose_if` check).
+- Added warnings for floating-point exception function calls (fenv.h) without enabling floating-point
+ exception behavior via the appropriate flags or pragmas on supported targets. (#GH128239)
+
### Improvements to Clang's time-trace
### Improvements to Coverage Mapping
>From 1a4018c95b49db1e6043482c4e3b4205149293ef Mon Sep 17 00:00:00 2001
From: Marcos Ramirez Joos <mramirezjoos.oss at proton.me>
Date: Wed, 1 Jul 2026 15:55:12 +0200
Subject: [PATCH 5/5] Fix conflict in serialization of fenv_t and fexcept_t
builtin types
---
clang/lib/AST/ASTContext.cpp | 21 +++++++------------
clang/utils/TableGen/ClangBuiltinsEmitter.cpp | 4 ++--
2 files changed, 10 insertions(+), 15 deletions(-)
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index a700143d1ba47..0632f20ee1c49 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -12921,20 +12921,15 @@ static QualType DecodeTypeFromStr(const char *&Str, const ASTContext &Context,
case 'm':
Type = Context.MFloat8Ty;
break;
- case 'T':
- switch (*Str++) {
- case 'x': {
- Type = Context.getfexcept_tType();
- break;
- }
- case 'e': {
- Type = Context.getfenv_tType();
- break;
- }
- default: {
- llvm_unreachable("Unexpected target builtin type");
- }
+ case 't':
+ Type = Context.getfexcept_tType();
+ if (Type.isNull()) {
+ Error = ASTContext::GE_Missing_fenv;
+ return {};
}
+ break;
+ case 'e':
+ Type = Context.getfenv_tType();
if (Type.isNull()) {
Error = ASTContext::GE_Missing_fenv;
return {};
diff --git a/clang/utils/TableGen/ClangBuiltinsEmitter.cpp b/clang/utils/TableGen/ClangBuiltinsEmitter.cpp
index 4ed98ddd3808a..8c85e18526e3d 100644
--- a/clang/utils/TableGen/ClangBuiltinsEmitter.cpp
+++ b/clang/utils/TableGen/ClangBuiltinsEmitter.cpp
@@ -380,8 +380,8 @@ class PrototypeParser {
.Case("uint64_t", "UWi")
.Case("void", "v")
.Case("wchar_t", "w")
- .Case("fexcept_t", "Tx")
- .Case("fenv_t", "Te")
+ .Case("fexcept_t", "t")
+ .Case("fenv_t", "e")
.Case("...", ".")
.Default("error");
if (ReturnTypeVal == "error")
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