[Clang] Fix warning for non std functions with name infinity (#123417)

Fix reporting diagnostic for non std functions that has the name
`infinity`

Fixes: #123231

clang/docs/ReleaseNotes.rst

@@ -798,6 +798,8 @@ Improvements to Clang's diagnostics
     }
 - Diagnose invalid declarators in the declaration of constructors and destructors (#GH121706).
 
+- Fix false positives warning for non-std functions with name `infinity` (#123231).
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/lib/Sema/SemaChecking.cpp

@@ -8454,24 +8454,41 @@ static bool IsInfOrNanFunction(StringRef calleeName, MathCheck Check) {
   llvm_unreachable("unknown MathCheck");
 }
 
+static bool IsInfinityFunction(const FunctionDecl *FDecl) {
+  if (FDecl->getName() != "infinity")
+    return false;
+
+  if (const CXXMethodDecl *MDecl = dyn_cast<CXXMethodDecl>(FDecl)) {
+    const CXXRecordDecl *RDecl = MDecl->getParent();
+    if (RDecl->getName() != "numeric_limits")
+      return false;
+
+    if (const NamespaceDecl *NSDecl =
+            dyn_cast<NamespaceDecl>(RDecl->getDeclContext()))
+      return NSDecl->isStdNamespace();
+  }
+
+  return false;
+}
+
 void Sema::CheckInfNaNFunction(const CallExpr *Call,
                                const FunctionDecl *FDecl) {
+  if (!FDecl->getIdentifier())
+    return;
+
   FPOptions FPO = Call->getFPFeaturesInEffect(getLangOpts());
-  bool HasIdentifier = FDecl->getIdentifier() != nullptr;
-  bool IsNaNOrIsUnordered =
-      IsStdFunction(FDecl, "isnan") || IsStdFunction(FDecl, "isunordered");
-  bool IsSpecialNaN =
-      HasIdentifier && IsInfOrNanFunction(FDecl->getName(), MathCheck::NaN);
-  if ((IsNaNOrIsUnordered || IsSpecialNaN) && FPO.getNoHonorNaNs()) {
+  if (FPO.getNoHonorNaNs() &&
+      (IsStdFunction(FDecl, "isnan") || IsStdFunction(FDecl, "isunordered") ||
+       IsInfOrNanFunction(FDecl->getName(), MathCheck::NaN))) {
     Diag(Call->getBeginLoc(), diag::warn_fp_nan_inf_when_disabled)
         << 1 << 0 << Call->getSourceRange();
-  } else {
-    bool IsInfOrIsFinite =
-        IsStdFunction(FDecl, "isinf") || IsStdFunction(FDecl, "isfinite");
-    bool IsInfinityOrIsSpecialInf =
-        HasIdentifier && ((FDecl->getName() == "infinity") ||
-                          IsInfOrNanFunction(FDecl->getName(), MathCheck::Inf));
-    if ((IsInfOrIsFinite || IsInfinityOrIsSpecialInf) && FPO.getNoHonorInfs())
+    return;
+  }
+
+  if (FPO.getNoHonorInfs() &&
+      (IsStdFunction(FDecl, "isinf") || IsStdFunction(FDecl, "isfinite") ||
+       IsInfinityFunction(FDecl) ||
+       IsInfOrNanFunction(FDecl->getName(), MathCheck::Inf))) {
     Diag(Call->getBeginLoc(), diag::warn_fp_nan_inf_when_disabled)
         << 0 << 0 << Call->getSourceRange();
   }

clang/test/Sema/warn-infinity-nan-disabled-lnx.cpp

@@ -45,7 +45,7 @@ namespace std __attribute__((__visibility__("default"))) {
   isnan(double __x);
   bool
   isnan(long double __x);
-bool
+  bool
   isfinite(float __x);
   bool
   isfinite(double __x);
@@ -57,12 +57,36 @@ bool
   isunordered(double __x, double __y);
   bool
   isunordered(long double __x, long double __y);
+
+template <class _Ty>
+class numeric_limits {
+public:
+    [[nodiscard]] static constexpr _Ty infinity() noexcept {
+        return _Ty();
+    }
+};
 } // namespace )
 }
 
 #define NAN (__builtin_nanf(""))
 #define INFINITY (__builtin_inff())
 
+template <>
+class std::numeric_limits<float>  {
+public:
+    [[nodiscard]] static constexpr float infinity() noexcept {
+        return __builtin_huge_val();
+    }
+};
+
+template <>
+class std::numeric_limits<double>  {
+public:
+    [[nodiscard]] static constexpr double infinity() noexcept {
+        return __builtin_huge_val();
+    }
+};
+
 template <class _Ty>
 class numeric_limits {
 public:
@@ -78,6 +102,7 @@ public:
         return __builtin_huge_val();
     }
 };
+
 template <>
 class numeric_limits<double>  {
 public:
@@ -86,6 +111,8 @@ public:
     }
 };
 
+double infinity() { return 0; }
+
 int compareit(float a, float b) {
   volatile int i, j, k, l, m, n, o, p;
 // no-inf-no-nan-warning@+4 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
@@ -225,11 +252,18 @@ int compareit(float a, float b) {
 
 // no-inf-no-nan-warning@+2 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
 // no-inf-warning@+1 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
-  double y = i * numeric_limits<double>::infinity();
+  double y = i * std::numeric_limits<double>::infinity();
+
+  y = i * numeric_limits<double>::infinity(); // expected-no-diagnostics
 
 // no-inf-no-nan-warning@+2 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
 // no-inf-warning@+1 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
-  j = numeric_limits<float>::infinity();
+  j = std::numeric_limits<float>::infinity();
+
+  j = numeric_limits<float>::infinity(); // expected-no-diagnostics
+
+  y = infinity(); // expected-no-diagnostics
+
   return 0;
 
 }

clang/test/Sema/warn-infinity-nan-disabled-win.cpp

@@ -48,7 +48,7 @@ namespace std __attribute__((__visibility__("default"))) {
   isnan(double __x);
   bool
   isnan(long double __x);
-bool
+  bool
   isfinite(float __x);
   bool
   isfinite(double __x);
@@ -60,12 +60,37 @@ bool
   isunordered(double __x, double __y);
   bool
   isunordered(long double __x, long double __y);
+
+template <class _Ty>
+class numeric_limits {
+public:
+    [[nodiscard]] static constexpr _Ty infinity() noexcept {
+        return _Ty();
+    }
+};
+
 } // namespace )
 }
 
 #define INFINITY ((float)(1e+300 * 1e+300))
 #define NAN      (-(float)(INFINITY * 0.0F))
 
+template <>
+class std::numeric_limits<float>  {
+public:
+    [[nodiscard]] static constexpr float infinity() noexcept {
+        return __builtin_huge_val();
+    }
+};
+
+template <>
+class std::numeric_limits<double>  {
+public:
+    [[nodiscard]] static constexpr double infinity() noexcept {
+        return __builtin_huge_val();
+    }
+};
+
 template <class _Ty>
 class numeric_limits {
 public:
@@ -81,6 +106,7 @@ public:
         return __builtin_huge_val();
     }
 };
+
 template <>
 class numeric_limits<double>  {
 public:
@@ -89,6 +115,8 @@ public:
     }
 };
 
+double infinity() { return 0; }
+
 int compareit(float a, float b) {
   volatile int i, j, k, l, m, n, o, p;
 // no-inf-no-nan-warning@+2 {{use of infinity via a macro is undefined behavior due to the currently enabled floating-point options}}
@@ -216,11 +244,18 @@ int compareit(float a, float b) {
 
 // no-inf-no-nan-warning@+2 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
 // no-inf-warning@+1 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
-  double y = i * numeric_limits<double>::infinity();
+  double y = i * std::numeric_limits<double>::infinity();
+
+  y = i * numeric_limits<double>::infinity(); // expected-no-diagnostics
 
 // no-inf-no-nan-warning@+2 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
 // no-inf-warning@+1 {{use of infinity is undefined behavior due to the currently enabled floating-point options}}
-  j = numeric_limits<float>::infinity();
+  j = std::numeric_limits<float>::infinity();
+
+  j = numeric_limits<float>::infinity(); // expected-no-diagnostics
+
+  y = infinity(); // expected-no-diagnostics
+
   return 0;
 
 }