[C23] Add *_NORM_MAX macros to <float.h> (#96643)

This adds the *_NORM_MAX macros to <float.h> for freestanding mode in Clang; the values were chosen based on the behavior seen coming from GCC and the values already produced for the *_MAX macros by Clang.
llvm · Jul 10, 2024 · 0e7590a · 0e7590a
1 parent 4c03207
commit 0e7590a
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Showing 6 changed files with 52 additions and 2 deletions.
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -355,6 +355,9 @@ C23 Feature Support
 - Clang now supports `N3017 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3017.htm>`_
   ``#embed`` - a scannable, tooling-friendly binary resource inclusion mechanism.
 
+- Added the ``FLT_NORM_MAX``, ``DBL_NORM_MAX``, and ``LDBL_NORM_MAX`` to the
+  freestanding implementation of ``<float.h>`` that ships with Clang.
+
 Non-comprehensive list of changes in this release
 -------------------------------------------------
 

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -113,7 +113,11 @@ static T PickFP(const llvm::fltSemantics *Sem, T IEEEHalfVal, T IEEESingleVal,
 
 static void DefineFloatMacros(MacroBuilder &Builder, StringRef Prefix,
                               const llvm::fltSemantics *Sem, StringRef Ext) {
-  const char *DenormMin, *Epsilon, *Max, *Min;
+  const char *DenormMin, *NormMax, *Epsilon, *Max, *Min;
+  NormMax = PickFP(Sem, "6.5504e+4", "3.40282347e+38",
+                   "1.7976931348623157e+308", "1.18973149535723176502e+4932",
+                   "8.98846567431157953864652595394501e+307",
+                   "1.18973149535723176508575932662800702e+4932");
   DenormMin = PickFP(Sem, "5.9604644775390625e-8", "1.40129846e-45",
                      "4.9406564584124654e-324", "3.64519953188247460253e-4951",
                      "4.94065645841246544176568792868221e-324",
@@ -144,6 +148,7 @@ static void DefineFloatMacros(MacroBuilder &Builder, StringRef Prefix,
   DefPrefix += "_";
 
   Builder.defineMacro(DefPrefix + "DENORM_MIN__", Twine(DenormMin)+Ext);
+  Builder.defineMacro(DefPrefix + "NORM_MAX__", Twine(NormMax)+Ext);
   Builder.defineMacro(DefPrefix + "HAS_DENORM__");
   Builder.defineMacro(DefPrefix + "DIG__", Twine(Digits));
   Builder.defineMacro(DefPrefix + "DECIMAL_DIG__", Twine(DecimalDigits));

diff --git a/clang/lib/Headers/float.h b/clang/lib/Headers/float.h
@@ -86,6 +86,12 @@
 #    undef DBL_HAS_SUBNORM
 #    undef LDBL_HAS_SUBNORM
 #  endif
+#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L) ||              \
+    !defined(__STRICT_ANSI__)
+#    undef FLT_NORM_MAX
+#    undef DBL_NORM_MAX
+#    undef LDBL_NORM_MAX
+#endif
 #endif
 
 #if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L) ||              \
@@ -166,6 +172,10 @@
    /* C23 5.2.5.3.3p29-30 */
 #  define INFINITY (__builtin_inff())
 #  define NAN (__builtin_nanf(""))
+   /* C23 5.2.5.3.3p32 */
+#  define FLT_NORM_MAX __FLT_NORM_MAX__
+#  define DBL_NORM_MAX __DBL_NORM_MAX__
+#  define LDBL_NORM_MAX __LDBL_NORM_MAX__
 #endif
 
 #ifdef __STDC_WANT_IEC_60559_TYPES_EXT__

diff --git a/clang/test/Headers/float.c b/clang/test/Headers/float.c
@@ -14,11 +14,13 @@
 // expected-no-diagnostics
 
 /* Basic floating point conformance checks against:
+    - C23 Final Std.
     - N1570 draft of C11 Std.
     - N1256 draft of C99 Std.
     - http://port70.net/~nsz/c/c89/c89-draft.html draft of C89/C90 Std.
 */
 /*
+    C23,    5.2.5.3.3p21,   pp. 25
     C11,    5.2.4.2.2p11,   pp. 30
     C99,    5.2.4.2.2p9,    pp. 25
     C89,    2.2.4.2
@@ -225,6 +227,22 @@
   _Static_assert(_Generic(INFINITY, float : 1, default : 0), ""); // finite-warning {{use of infinity via a macro is undefined behavior due to the currently enabled floating-point options}}
   _Static_assert(_Generic(NAN, float : 1, default : 0), ""); // finite-warning {{use of NaN is undefined behavior due to the currently enabled floating-point options}} \
                                                                 finite-warning {{use of NaN via a macro is undefined behavior due to the currently enabled floating-point options}}
+
+#ifndef FLT_NORM_MAX
+  #error "Mandatory macro FLT_NORM_MAX is missing."
+#else
+  _Static_assert(FLT_NORM_MAX >= 1.0E+37F, "Mandatory macro FLT_NORM_MAX is invalid.");
+#endif
+#ifndef DBL_NORM_MAX
+  #error "Mandatory macro DBL_NORM_MAX is missing."
+#else
+  _Static_assert(DBL_NORM_MAX >= 1.0E+37, "Mandatory macro DBL_NORM_MAX is invalid.");
+#endif
+#ifndef LDBL_NORM_MAX
+  #error "Mandatory macro LDBL_NORM_MAX is missing."
+#else
+  _Static_assert(LDBL_NORM_MAX >= 1.0E+37L, "Mandatory macro LDBL_NORM_MAX is invalid.");
+#endif
 #else
   #ifdef INFINITY
     #error "Macro INFINITY should not be defined."
@@ -271,8 +289,14 @@ _Static_assert(FLT_MAX_10_EXP == __FLT_MAX_10_EXP__, "");
 _Static_assert(DBL_MAX_10_EXP == __DBL_MAX_10_EXP__, "");
 _Static_assert(LDBL_MAX_10_EXP == __LDBL_MAX_10_EXP__, "");
 
-#if (__STDC_VERSION__ >= 202311L || !defined(__STRICT_ANSI__)) && __FINITE_MATH_ONLY__ == 0
+#if __STDC_VERSION__ >= 202311L || !defined(__STRICT_ANSI__)
+_Static_assert(FLT_NORM_MAX == __FLT_NORM_MAX__, "");
+_Static_assert(DBL_NORM_MAX == __DBL_NORM_MAX__, "");
+_Static_assert(LDBL_NORM_MAX == __LDBL_NORM_MAX__, "");
+
+#if __FINITE_MATH_ONLY__ == 0
 // Ensure INFINITY and NAN are suitable for use in a constant expression.
 float f1 = INFINITY;
 float f2 = NAN;
 #endif
+#endif
diff --git a/clang/test/Preprocessor/init-aarch64.c b/clang/test/Preprocessor/init-aarch64.c
@@ -74,6 +74,7 @@
 // AARCH64-NEXT: #define __DBL_MIN_10_EXP__ (-307)
 // AARCH64-NEXT: #define __DBL_MIN_EXP__ (-1021)
 // AARCH64-NEXT: #define __DBL_MIN__ 2.2250738585072014e-308
+// AARCH64-NEXT: #define __DBL_NORM_MAX__ 1.7976931348623157e+308
 // AARCH64-NEXT: #define __DECIMAL_DIG__ __LDBL_DECIMAL_DIG__
 // AARCH64-NEXT: #define __ELF__ 1
 // AARCH64-NEXT: #define __FINITE_MATH_ONLY__ 0
@@ -91,6 +92,7 @@
 // AARCH64-NEXT: #define __FLT16_MIN_10_EXP__ (-4)
 // AARCH64-NEXT: #define __FLT16_MIN_EXP__ (-13)
 // AARCH64-NEXT: #define __FLT16_MIN__ 6.103515625e-5F16
+// AARCH64-NEXT: #define __FLT16_NORM_MAX__ 6.5504e+4F16
 // AARCH64-NEXT: #define __FLT_DECIMAL_DIG__ 9
 // AARCH64-NEXT: #define __FLT_DENORM_MIN__ 1.40129846e-45F
 // AARCH64-NEXT: #define __FLT_DIG__ 6
@@ -105,6 +107,7 @@
 // AARCH64-NEXT: #define __FLT_MIN_10_EXP__ (-37)
 // AARCH64-NEXT: #define __FLT_MIN_EXP__ (-125)
 // AARCH64-NEXT: #define __FLT_MIN__ 1.17549435e-38F
+// AARCH64-NEXT: #define __FLT_NORM_MAX__ 3.40282347e+38F
 // AARCH64-NEXT: #define __FLT_RADIX__ 2
 // AARCH64-NEXT: #define __FPCLASS_NEGINF 0x0004
 // AARCH64-NEXT: #define __FPCLASS_NEGNORMAL 0x0008
@@ -216,6 +219,7 @@
 // AARCH64-NEXT: #define __LDBL_MIN_10_EXP__ (-4931)
 // AARCH64-NEXT: #define __LDBL_MIN_EXP__ (-16381)
 // AARCH64-NEXT: #define __LDBL_MIN__ 3.36210314311209350626267781732175260e-4932L
+// AARCH64-NEXT: #define __LDBL_NORM_MAX__ 1.18973149535723176508575932662800702e+4932L
 // AARCH64_LE-NEXT: #define __LITTLE_ENDIAN__ 1
 // AARCH64-NEXT: #define __LLONG_WIDTH__ 64
 // AARCH64-NEXT: #define __LONG_LONG_MAX__ 9223372036854775807LL

diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
@@ -1648,6 +1648,7 @@
 // WEBASSEMBLY-NEXT:#define __DBL_MIN_10_EXP__ (-307)
 // WEBASSEMBLY-NEXT:#define __DBL_MIN_EXP__ (-1021)
 // WEBASSEMBLY-NEXT:#define __DBL_MIN__ 2.2250738585072014e-308
+// WEBASSEMBLY-NEXT:#define __DBL_NORM_MAX__ 1.7976931348623157e+308
 // WEBASSEMBLY-NEXT:#define __DECIMAL_DIG__ __LDBL_DECIMAL_DIG__
 // WEBASSEMBLY-NOT:#define __ELF__
 // EMSCRIPTEN-THREADS-NEXT:#define __EMSCRIPTEN_PTHREADS__ 1
@@ -1668,6 +1669,7 @@
 // WEBASSEMBLY-NOT:#define __FLT16_MIN_10_EXP__
 // WEBASSEMBLY-NOT:#define __FLT16_MIN_EXP__
 // WEBASSEMBLY-NOT:#define __FLT16_MIN__
+// WEBASSEMBLY-NOT:#define __FLT16_NORM_MAX__
 // WEBASSEMBLY-NEXT:#define __FLT_DECIMAL_DIG__ 9
 // WEBASSEMBLY-NEXT:#define __FLT_DENORM_MIN__ 1.40129846e-45F
 // WEBASSEMBLY-NEXT:#define __FLT_DIG__ 6
@@ -1682,6 +1684,7 @@
 // WEBASSEMBLY-NEXT:#define __FLT_MIN_10_EXP__ (-37)
 // WEBASSEMBLY-NEXT:#define __FLT_MIN_EXP__ (-125)
 // WEBASSEMBLY-NEXT:#define __FLT_MIN__ 1.17549435e-38F
+// WEBASSEMBLY-NEXT:#define __FLT_NORM_MAX__ 3.40282347e+38F
 // WEBASSEMBLY-NEXT:#define __FLT_RADIX__ 2
 // WEBASSEMBLY-NEXT:#define __FPCLASS_NEGINF 0x0004
 // WEBASSEMBLY-NEXT:#define __FPCLASS_NEGNORMAL 0x0008
@@ -1806,6 +1809,7 @@
 // WEBASSEMBLY-NEXT:#define __LDBL_MIN_10_EXP__ (-4931)
 // WEBASSEMBLY-NEXT:#define __LDBL_MIN_EXP__ (-16381)
 // WEBASSEMBLY-NEXT:#define __LDBL_MIN__ 3.36210314311209350626267781732175260e-4932L
+// WEBASSEMBLY-NEXT:#define __LDBL_NORM_MAX__ 1.18973149535723176508575932662800702e+4932L
 // WEBASSEMBLY-NEXT:#define __LITTLE_ENDIAN__ 1
 // WEBASSEMBLY-NEXT:#define __LLONG_WIDTH__ 64
 // WEBASSEMBLY-NEXT:#define __LONG_LONG_MAX__ 9223372036854775807LL