diff --git a/libc/config/linux/api.td b/libc/config/linux/api.td
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -71,10 +71,53 @@
   ];
 }
 
+def MathErrHandlingMacro : MacroDef<"math_errhandling"> {
+  let Defn = [{
+    #ifndef math_errhandling
+    #ifdef __FAST_MATH__
+    #define math_errhandling 0
+    #elif defined __NO_MATH_ERRNO__
+    #define math_errhandling (MATH_ERREXCEPT)
+    #else
+    #define math_errhandling (MATH_ERRNO | MATH_ERREXCEPT)
+    #endif
+    #endif // math_errhandling not defined
+  }];
+}
+
+def IsFiniteMacro : MacroDef<"isfinite"> {
+  let Defn = [{
+    #define isfinite(x) __builtin_isfinite(x)
+  }];
+}
+
+def IsInfMacro : MacroDef<"isinf"> {
+  let Defn = [{
+    #define isinf(x) __builtin_isinf(x)
+  }];
+}
+
+def IsNanMacro : MacroDef<"isnan"> {
+  let Defn = [{
+    #define isnan(x) __builtin_isnan(x)
+  }];
+}
+
 def MathAPI : PublicAPI<"math.h"> {
+  let Macros = [
+    SimpleMacroDef<"MATH_ERRNO", "1">,
+    SimpleMacroDef<"MATH_ERREXCEPT", "2">,
+    MathErrHandlingMacro,
+
+    SimpleMacroDef<"INFINITY", "__builtin_inff()">,
+    SimpleMacroDef<"NAN", "__builtin_nanf(\"\")">,
+
+    IsFiniteMacro,
+    IsInfMacro,
+    IsNanMacro,
+  ];
   let Functions = [
-   "acos",
-   "acosl",
+   "round",
   ];
 }
 
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -19,10 +19,10 @@
     llvm_libc_common_h
 )
 
-add_header(
+add_gen_header(
   math_h
-  HDR
-    math.h
+  DEF_FILE math.h.def
+  GEN_HDR math.h
   DEPENDS
     llvm_libc_common_h
 )
diff --git a/libc/include/math.h b/libc/include/math.h
deleted file mode 100644
--- a/libc/include/math.h
+++ /dev/null
@@ -1,360 +0,0 @@
-//===----------------- C standard library header math.h -----------------*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_LIBC_MATH_H
-#define LLVM_LIBC_MATH_H
-
-#include <__llvm-libc-common.h>
-
-__BEGIN_C_DECLS
-
-double acos(double);
-
-float acosf(float);
-
-long double acosl(long double);
-
-double asin(double);
-
-float asinf(float);
-
-long double asinl(long double);
-
-double atan(double);
-
-float atanf(float);
-
-long double atanl(long double);
-
-double atan2(double, double);
-
-float atan2f(float, float);
-
-long double atan2l(long double, long double);
-
-double cos(double);
-
-float cosf(float);
-
-long double cosl(long double);
-
-double sin(double);
-
-float sinf(float);
-
-long double sinl(long double);
-
-double tan(double);
-
-float tanf(float);
-
-long double tanl(long double);
-
-double acosh(double);
-
-float acoshf(float);
-
-long double acoshl(long double);
-
-double asinh(double);
-
-float asinhf(float);
-
-long double asinhl(long double);
-
-double atanh(double);
-
-float atanhf(float);
-
-long double atanhl(long double);
-
-double cosh(double);
-
-float coshf(float);
-
-long double coshl(long double);
-
-double sinh(double);
-
-float sinhf(float);
-
-long double sinhl(long double);
-
-double tanh(double);
-
-float tanhf(float);
-
-long double tanhl(long double);
-
-double exp(double);
-
-float expf(float);
-
-long double expl(long double);
-
-double exp2(double);
-
-float exp2f(float);
-
-long double exp2l(long double);
-
-double expm1(double);
-
-float expm1f(float);
-
-long double expm1l(long double);
-
-double frexp(double, int);
-
-float frexpf(float, int);
-
-long double frexpl(long double, int);
-
-int ilogb(double);
-
-int ilogbf(float);
-
-int ilogbl(long double);
-
-double ldexp(double, int);
-
-float ldexpf(float, int);
-
-long double ldexpl(long double, int);
-
-double log(double);
-
-float logf(float);
-
-long double logl(long double);
-
-double log10(double);
-
-float log10f(float);
-
-long double log10l(long double);
-
-double log1p(double);
-
-float log1pf(float);
-
-long double log1pl(long double);
-
-double log2(double);
-
-float log2f(float);
-
-long double log2l(long double);
-
-double logb(double);
-
-float logbf(float);
-
-long double logbl(long double);
-
-double modf(double, double);
-
-float modff(float, float);
-
-long double modfl(long double, long double);
-
-double scalbn(double, int);
-
-float scalbnf(float, int);
-
-long double scalbnl(long double, int);
-
-double scalbln(double, long int);
-
-float scalblnf(float, long int);
-
-long double scalblnl(long double, long int);
-
-double cbrt(double);
-
-float cbrtf(float);
-
-long double cbrtl(long double);
-
-double fabs(double);
-
-float fabsf(float);
-
-long double fabsl(long double);
-
-double hypot(double, double);
-
-float hypotf(float, float);
-
-long double hypotl(long double, long double);
-
-double pow(double, double);
-
-float powf(float, float);
-
-long double powl(long double, long double);
-
-double sqrt(double);
-
-float sqrtf(float);
-
-long double sqrtl(long double);
-
-double erf(double);
-
-float erff(float);
-
-long double erfl(long double);
-
-double erfc(double);
-
-float erfcf(float);
-
-long double erfcl(long double);
-
-double lgamma(double);
-
-float lgammaf(float);
-
-long double lgammal(long double);
-
-double tgamma(double);
-
-float tgammaf(float);
-
-long double tgammal(long double);
-
-double ceil(double);
-
-float ceilf(float);
-
-long double ceill(long double);
-
-double floor(double);
-
-float floorf(float);
-
-long double floorl(long double);
-
-double nearbyint(double);
-
-float nearbyintf(float);
-
-long double nearbyintl(long double);
-
-double rint(double);
-
-float rintf(float);
-
-long double rintl(long double);
-
-long int lrint(double);
-
-long int lrintf(float);
-
-long int lrintl(long double);
-
-long long int llrint(double);
-
-long long int llrintf(float);
-
-long long int llrintl(long double);
-
-double round(double);
-
-float roundf(float);
-
-long double roundl(long double);
-
-long int lround(double);
-
-long int lroundf(float);
-
-long int lroundl(long double);
-
-long long int llround(double);
-
-long long int llroundf(float);
-
-long long int llroundl(long double);
-
-double trunc(double);
-
-float truncf(float);
-
-long double truncl(long double);
-
-double fmod(double, double);
-
-float fmodf(float, float);
-
-long double fmodl(long double, long double);
-
-double remainder(double, double);
-
-float remainderf(float, float);
-
-long double remainderl(long double, long double);
-
-double remquo(double, double, int);
-
-float remquof(float, float, int);
-
-long double remquol(long double, long double, int);
-
-double copysign(double, double);
-
-float copysignf(float, float);
-
-long double copysignl(long double, long double);
-
-double nan(const char);
-
-float nanf(const char);
-
-long double nanl(const char);
-
-double nextafter(double, double);
-
-float nextafterf(float, float);
-
-long double nextafterl(long double, long double);
-
-double nexttoward(double, long double);
-
-float nexttowardf(float, long double);
-
-long double nexttowardl(long double, long double);
-
-double fdim(double, double);
-
-float fdimf(float, float);
-
-long double fdiml(long double, long double);
-
-double fmax(double, double);
-
-double fmaxf(double, double);
-
-double fmaxl(double, double);
-
-double fmin(double, double);
-
-float fminf(float, float);
-
-long double fminl(long double, long double);
-
-double fma(double, double, double);
-
-float fmaf(float, float, float);
-
-long double fmal(long double, long double, long double);
-
-__END_C_DECLS
-
-#endif // LLVM_LIBC_MATH_H
diff --git a/libc/include/math.h.def b/libc/include/math.h.def
new file mode 100644
--- /dev/null
+++ b/libc/include/math.h.def
@@ -0,0 +1,16 @@
+//===----------------- C standard library header math.h -----------------*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_MATH_H
+#define LLVM_LIBC_MATH_H
+
+#include <__llvm-libc-common.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_MATH_H
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -160,15 +160,28 @@
 
   HeaderSpec Math = HeaderSpec<
       "math.h",
-      [], // Macros
+      [
+          Macro<"MATH_ERRNO">,
+          Macro<"MATH_ERREXCEPT">,
+          Macro<"math_errhandling">,
+
+          Macro<"INFINITY">,
+          Macro<"NAN">,
+
+          Macro<"isfinite">,
+          Macro<"isinf">,
+          Macro<"isnan">,
+      ],
       [
           NamedType<"float_t">,
           NamedType<"double_t">,
       ],
       [], // Enumerations
       [
-          FunctionSpec<"acos", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
-          FunctionSpec<"acosl", RetValSpec<LongDoubleType>, [ArgSpec<LongDoubleType>]>,
+          FunctionSpec<"cosf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
+          FunctionSpec<"sinf", RetValSpec<FloatType>, [ArgSpec<FloatType>]>,
+
+          FunctionSpec<"round", RetValSpec<DoubleType>, [ArgSpec<DoubleType>]>,
       ]
   >;