diff --git a/source/expressions.tex b/source/expressions.tex
index 8a3fab39bf..3962861606 100644
--- a/source/expressions.tex
+++ b/source/expressions.tex
@@ -7393,7 +7393,11 @@
 an \grammarterm{asm-declaration}\iref{dcl.asm};
 
 \item
-an invocation of the \tcode{va_arg} macro\iref{cstdarg.syn}; or
+an invocation of the \tcode{va_arg} macro\iref{cstdarg.syn};
+
+\item
+a non-constant library call\iref{defns.nonconst.libcall};
+or
 
 \item
 a \keyword{goto} statement\iref{stmt.goto}.
diff --git a/source/intro.tex b/source/intro.tex
index cbee223c7b..4bde4a91a0 100644
--- a/source/intro.tex
+++ b/source/intro.tex
@@ -423,6 +423,12 @@
 sequence of one or more bytes representing
 the code unit sequence for an encoded character of the execution character set
 
+\indexdefn{library call!non-constant}%
+\definition{non-constant library call}{defns.nonconst.libcall}
+invocation of a library function that,
+as part of evaluating any expression \tcode{E},
+prevents \tcode{E} from being a core constant expression
+
 \definition{NTCTS}{defns.ntcts}
 \defncontext{library}
 \indexdefn{NTCTS}%
diff --git a/source/lib-intro.tex b/source/lib-intro.tex
index a4e4fe6889..bf960caa7e 100644
--- a/source/lib-intro.tex
+++ b/source/lib-intro.tex
@@ -136,6 +136,30 @@
 ISO C \tcode{restrict} qualifier)
 are the same unless otherwise stated.
 
+\pnum
+A call to a C standard library function is
+a non-constant library call\iref{defns.nonconst.libcall}
+if it raises a floating-point exception other than \tcode{FE_INEXACT}.
+The semantics of a call to a C standard library function
+evaluated as a core constant expression
+are those specified in Annex F of the C standard
+\begin{footnote}
+See also ISO/IEC 9899:2018 section 7.6.
+\end{footnote}
+to the extent applicable to the floating-point types\iref{basic.fundamental}
+that are parameter types of the called function.
+\begin{note}
+Annex F specifies
+the conditions under which floating-point exceptions are raised and
+the behavior when NaNs and/or infinities are passed as arguments.
+\end{note}
+\begin{note}
+Equivalently, a call to a C standard library function is
+a non-constant library call
+if \tcode{errno} is set
+when \tcode{math_errhandling \& MATH_ERRNO} is \tcode{true}.
+\end{note}
+
 \rSec1[description]{Method of description}
 
 \rSec2[description.general]{General}
diff --git a/source/numerics.tex b/source/numerics.tex
index 9448d6a94a..dcb43333ab 100644
--- a/source/numerics.tex
+++ b/source/numerics.tex
@@ -9538,23 +9538,23 @@
   float expm1f(float x);
   long double expm1l(long double x);
 
-  float frexp(float value, int* exp);   // see \ref{library.c}
-  double frexp(double value, int* exp);
-  long double frexp(long double value, int* exp);   // see \ref{library.c}
-  float frexpf(float value, int* exp);
-  long double frexpl(long double value, int* exp);
-
-  int ilogb(float x);                   // see \ref{library.c}
-  int ilogb(double x);
-  int ilogb(long double x);             // see \ref{library.c}
-  int ilogbf(float x);
-  int ilogbl(long double x);
-
-  float ldexp(float x, int exp);        // see \ref{library.c}
-  double ldexp(double x, int exp);
-  long double ldexp(long double x, int exp);    // see \ref{library.c}
-  float ldexpf(float x, int exp);
-  long double ldexpl(long double x, int exp);
+  constexpr float frexp(float value, int* exp);         // see \ref{library.c}
+  constexpr double frexp(double value, int* exp);
+  constexpr long double frexp(long double value, int* exp);     // see \ref{library.c}
+  constexpr float frexpf(float value, int* exp);
+  constexpr long double frexpl(long double value, int* exp);
+
+  constexpr int ilogb(float x);                         // see \ref{library.c}
+  constexpr int ilogb(double x);
+  constexpr int ilogb(long double x);                   // see \ref{library.c}
+  constexpr int ilogbf(float x);
+  constexpr int ilogbl(long double x);
+
+  constexpr float ldexp(float x, int exp);              // see \ref{library.c}
+  constexpr double ldexp(double x, int exp);
+  constexpr long double ldexp(long double x, int exp);  // see \ref{library.c}
+  constexpr float ldexpf(float x, int exp);
+  constexpr long double ldexpl(long double x, int exp);
 
   float log(float x);                   // see \ref{library.c}
   double log(double x);
@@ -9580,29 +9580,29 @@
   float log2f(float x);
   long double log2l(long double x);
 
-  float logb(float x);                  // see \ref{library.c}
-  double logb(double x);
-  long double logb(long double x);      // see \ref{library.c}
-  float logbf(float x);
-  long double logbl(long double x);
-
-  float modf(float value, float* iptr); // see \ref{library.c}
-  double modf(double value, double* iptr);
-  long double modf(long double value, long double* iptr);   // see \ref{library.c}
-  float modff(float value, float* iptr);
-  long double modfl(long double value, long double* iptr);
-
-  float scalbn(float x, int n);         // see \ref{library.c}
-  double scalbn(double x, int n);
-  long double scalbn(long double x, int n);     // see \ref{library.c}
-  float scalbnf(float x, int n);
-  long double scalbnl(long double x, int n);
-
-  float scalbln(float x, long int n);   // see \ref{library.c}
-  double scalbln(double x, long int n);
-  long double scalbln(long double x, long int n);   // see \ref{library.c}
-  float scalblnf(float x, long int n);
-  long double scalblnl(long double x, long int n);
+  constexpr float logb(float x);                // see \ref{library.c}
+  constexpr double logb(double x);
+  constexpr long double logb(long double x);    // see \ref{library.c}
+  constexpr float logbf(float x);
+  constexpr long double logbl(long double x);
+
+  constexpr float modf(float value, float* iptr);   // see \ref{library.c}
+  constexpr double modf(double value, double* iptr);
+  constexpr long double modf(long double value, long double* iptr); // see \ref{library.c}
+  constexpr float modff(float value, float* iptr);
+  constexpr long double modfl(long double value, long double* iptr);
+
+  constexpr float scalbn(float x, int n);           // see \ref{library.c}
+  constexpr double scalbn(double x, int n);
+  constexpr long double scalbn(long double x, int n);       // see \ref{library.c}
+  constexpr float scalbnf(float x, int n);
+  constexpr long double scalbnl(long double x, int n);
+
+  constexpr float scalbln(float x, long int n);     // see \ref{library.c}
+  constexpr double scalbln(double x, long int n);
+  constexpr long double scalbln(long double x, long int n); // see \ref{library.c}
+  constexpr float scalblnf(float x, long int n);
+  constexpr long double scalblnl(long double x, long int n);
 
   float cbrt(float x);                  // see \ref{library.c}
   double cbrt(double x);
@@ -9611,18 +9611,18 @@
   long double cbrtl(long double x);
 
   // \ref{c.math.abs}, absolute values
-  int abs(int j);
-  long int abs(long int j);
-  long long int abs(long long int j);
-  float abs(float j);
-  double abs(double j);
-  long double abs(long double j);
-
-  float fabs(float x);                  // see \ref{library.c}
-  double fabs(double x);
-  long double fabs(long double x);      // see \ref{library.c}
-  float fabsf(float x);
-  long double fabsl(long double x);
+  constexpr int abs(int j);
+  constexpr long int abs(long int j);
+  constexpr long long int abs(long long int j);
+  constexpr float abs(float j);
+  constexpr double abs(double j);
+  constexpr long double abs(long double j);
+
+  constexpr float fabs(float x);                // see \ref{library.c}
+  constexpr double fabs(double x);
+  constexpr long double fabs(long double x);    // see \ref{library.c}
+  constexpr float fabsf(float x);
+  constexpr long double fabsl(long double x);
 
   float hypot(float x, float y);        // see \ref{library.c}
   double hypot(double x, double y);
@@ -9671,17 +9671,17 @@
   float tgammaf(float x);
   long double tgammal(long double x);
 
-  float ceil(float x);                  // see \ref{library.c}
-  double ceil(double x);
-  long double ceil(long double x);      // see \ref{library.c}
-  float ceilf(float x);
-  long double ceill(long double x);
+  constexpr float ceil(float x);                // see \ref{library.c}
+  constexpr double ceil(double x);
+  constexpr long double ceil(long double x);    // see \ref{library.c}
+  constexpr float ceilf(float x);
+  constexpr long double ceill(long double x);
 
-  float floor(float x);                 // see \ref{library.c}
-  double floor(double x);
-  long double floor(long double x);     // see \ref{library.c}
-  float floorf(float x);
-  long double floorl(long double x);
+  constexpr float floor(float x);               // see \ref{library.c}
+  constexpr double floor(double x);
+  constexpr long double floor(long double x);   // see \ref{library.c}
+  constexpr float floorf(float x);
+  constexpr long double floorl(long double x);
 
   float nearbyint(float x);             // see \ref{library.c}
   double nearbyint(double x);
@@ -9707,93 +9707,93 @@
   long long int llrintf(float x);
   long long int llrintl(long double x);
 
-  float round(float x);                 // see \ref{library.c}
-  double round(double x);
-  long double round(long double x);     // see \ref{library.c}
-  float roundf(float x);
-  long double roundl(long double x);
-
-  long int lround(float x);             // see \ref{library.c}
-  long int lround(double x);
-  long int lround(long double x);       // see \ref{library.c}
-  long int lroundf(float x);
-  long int lroundl(long double x);
-
-  long long int llround(float x);       // see \ref{library.c}
-  long long int llround(double x);
-  long long int llround(long double x); // see \ref{library.c}
-  long long int llroundf(float x);
-  long long int llroundl(long double x);
-
-  float trunc(float x);                 // see \ref{library.c}
-  double trunc(double x);
-  long double trunc(long double x);     // see \ref{library.c}
-  float truncf(float x);
-  long double truncl(long double x);
-
-  float fmod(float x, float y);         // see \ref{library.c}
-  double fmod(double x, double y);
-  long double fmod(long double x, long double y);   // see \ref{library.c}
-  float fmodf(float x, float y);
-  long double fmodl(long double x, long double y);
-
-  float remainder(float x, float y);    // see \ref{library.c}
-  double remainder(double x, double y);
-  long double remainder(long double x, long double y);  // see \ref{library.c}
-  float remainderf(float x, float y);
-  long double remainderl(long double x, long double y);
-
-  float remquo(float x, float y, int* quo);     // see \ref{library.c}
-  double remquo(double x, double y, int* quo);
-  long double remquo(long double x, long double y, int* quo);   // see \ref{library.c}
-  float remquof(float x, float y, int* quo);
-  long double remquol(long double x, long double y, int* quo);
-
-  float copysign(float x, float y);     // see \ref{library.c}
-  double copysign(double x, double y);
-  long double copysign(long double x, long double y);   // see \ref{library.c}
-  float copysignf(float x, float y);
-  long double copysignl(long double x, long double y);
+  constexpr float round(float x);               // see \ref{library.c}
+  constexpr double round(double x);
+  constexpr long double round(long double x);   // see \ref{library.c}
+  constexpr float roundf(float x);
+  constexpr long double roundl(long double x);
+
+  constexpr long int lround(float x);           // see \ref{library.c}
+  constexpr long int lround(double x);
+  constexpr long int lround(long double x);     // see \ref{library.c}
+  constexpr long int lroundf(float x);
+  constexpr long int lroundl(long double x);
+
+  constexpr long long int llround(float x);         // see \ref{library.c}
+  constexpr long long int llround(double x);
+  constexpr long long int llround(long double x);   // see \ref{library.c}
+  constexpr long long int llroundf(float x);
+  constexpr long long int llroundl(long double x);
+
+  constexpr float trunc(float x);               // see \ref{library.c}
+  constexpr double trunc(double x);
+  constexpr long double trunc(long double x);   // see \ref{library.c}
+  constexpr float truncf(float x);
+  constexpr long double truncl(long double x);
+
+  constexpr float fmod(float x, float y);       // see \ref{library.c}
+  constexpr double fmod(double x, double y);
+  constexpr long double fmod(long double x, long double y);     // see \ref{library.c}
+  constexpr float fmodf(float x, float y);
+  constexpr long double fmodl(long double x, long double y);
+
+  constexpr float remainder(float x, float y);  // see \ref{library.c}
+  constexpr double remainder(double x, double y);
+  constexpr long double remainder(long double x, long double y);    // see \ref{library.c}
+  constexpr float remainderf(float x, float y);
+  constexpr long double remainderl(long double x, long double y);
+
+  constexpr float remquo(float x, float y, int* quo);   // see \ref{library.c}
+  constexpr double remquo(double x, double y, int* quo);
+  constexpr long double remquo(long double x, long double y, int* quo);     // see \ref{library.c}
+  constexpr float remquof(float x, float y, int* quo);
+  constexpr long double remquol(long double x, long double y, int* quo);
+
+  constexpr float copysign(float x, float y);   // see \ref{library.c}
+  constexpr double copysign(double x, double y);
+  constexpr long double copysign(long double x, long double y);     // see \ref{library.c}
+  constexpr float copysignf(float x, float y);
+  constexpr long double copysignl(long double x, long double y);
 
   double nan(const char* tagp);
   float nanf(const char* tagp);
   long double nanl(const char* tagp);
 
-  float nextafter(float x, float y);    // see \ref{library.c}
-  double nextafter(double x, double y);
-  long double nextafter(long double x, long double y);  // see \ref{library.c}
-  float nextafterf(float x, float y);
-  long double nextafterl(long double x, long double y);
-
-  float nexttoward(float x, long double y);     // see \ref{library.c}
-  double nexttoward(double x, long double y);
-  long double nexttoward(long double x, long double y);     // see \ref{library.c}
-  float nexttowardf(float x, long double y);
-  long double nexttowardl(long double x, long double y);
-
-  float fdim(float x, float y);         // see \ref{library.c}
-  double fdim(double x, double y);
-  long double fdim(long double x, long double y);   // see \ref{library.c}
-  float fdimf(float x, float y);
-  long double fdiml(long double x, long double y);
-
-  float fmax(float x, float y);         // see \ref{library.c}
-  double fmax(double x, double y);
-  long double fmax(long double x, long double y);   // see \ref{library.c}
-  float fmaxf(float x, float y);
-  long double fmaxl(long double x, long double y);
-
-  float fmin(float x, float y);         // see \ref{library.c}
-  double fmin(double x, double y);
-  long double fmin(long double x, long double y);   // see \ref{library.c}
-  float fminf(float x, float y);
-  long double fminl(long double x, long double y);
-
-  float fma(float x, float y, float z); // see \ref{library.c}
-  double fma(double x, double y, double z);
-  long double fma(long double x, long double y, long double z); // see \ref{library.c}
-  float fmaf(float x, float y, float z);
-  long double fmal(long double x, long double y, long double z);
+  constexpr float nextafter(float x, float y);      // see \ref{library.c}
+  constexpr double nextafter(double x, double y);
+  constexpr long double nextafter(long double x, long double y);    // see \ref{library.c}
+  constexpr float nextafterf(float x, float y);
+  constexpr long double nextafterl(long double x, long double y);
+
+  constexpr float nexttoward(float x, long double y);       // see \ref{library.c}
+  constexpr double nexttoward(double x, long double y);
+  constexpr long double nexttoward(long double x, long double y);   // see \ref{library.c}
+  constexpr float nexttowardf(float x, long double y);
+  constexpr long double nexttowardl(long double x, long double y);
+
+  constexpr float fdim(float x, float y);       // see \ref{library.c}
+  constexpr double fdim(double x, double y);
+  constexpr long double fdim(long double x, long double y);     // see \ref{library.c}
+  constexpr float fdimf(float x, float y);
+  constexpr long double fdiml(long double x, long double y);
+
+  constexpr float fmax(float x, float y);       // see \ref{library.c}
+  constexpr double fmax(double x, double y);
+  constexpr long double fmax(long double x, long double y);     // see \ref{library.c}
+  constexpr float fmaxf(float x, float y);
+  constexpr long double fmaxl(long double x, long double y);
+
+  constexpr float fmin(float x, float y);       // see \ref{library.c}
+  constexpr double fmin(double x, double y);
+  constexpr long double fmin(long double x, long double y);     // see \ref{library.c}
+  constexpr float fminf(float x, float y);
+  constexpr long double fminl(long double x, long double y);
+
+  constexpr float fma(float x, float y, float z);   // see \ref{library.c}
+  constexpr double fma(double x, double y, double z);
+  constexpr long double fma(long double x, long double y, long double z);   // see \ref{library.c}
+  constexpr float fmaf(float x, float y, float z);
+  constexpr long double fmal(long double x, long double y, long double z);
 
   // \ref{c.math.lerp}, linear interpolation
   constexpr float lerp(float a, float b, float t) noexcept;
@@ -9801,53 +9801,53 @@
   constexpr long double lerp(long double a, long double b, long double t) noexcept;
 
   // \ref{c.math.fpclass}, classification / comparison functions
-  int fpclassify(float x);
-  int fpclassify(double x);
-  int fpclassify(long double x);
+  constexpr int fpclassify(float x);
+  constexpr int fpclassify(double x);
+  constexpr int fpclassify(long double x);
 
-  bool isfinite(float x);
-  bool isfinite(double x);
-  bool isfinite(long double x);
+  constexpr bool isfinite(float x);
+  constexpr bool isfinite(double x);
+  constexpr bool isfinite(long double x);
 
-  bool isinf(float x);
-  bool isinf(double x);
-  bool isinf(long double x);
+  constexpr bool isinf(float x);
+  constexpr bool isinf(double x);
+  constexpr bool isinf(long double x);
 
-  bool isnan(float x);
-  bool isnan(double x);
-  bool isnan(long double x);
+  constexpr bool isnan(float x);
+  constexpr bool isnan(double x);
+  constexpr bool isnan(long double x);
 
-  bool isnormal(float x);
-  bool isnormal(double x);
-  bool isnormal(long double x);
+  constexpr bool isnormal(float x);
+  constexpr bool isnormal(double x);
+  constexpr bool isnormal(long double x);
 
-  bool signbit(float x);
-  bool signbit(double x);
-  bool signbit(long double x);
+  constexpr bool signbit(float x);
+  constexpr bool signbit(double x);
+  constexpr bool signbit(long double x);
 
-  bool isgreater(float x, float y);
-  bool isgreater(double x, double y);
-  bool isgreater(long double x, long double y);
+  constexpr bool isgreater(float x, float y);
+  constexpr bool isgreater(double x, double y);
+  constexpr bool isgreater(long double x, long double y);
 
-  bool isgreaterequal(float x, float y);
-  bool isgreaterequal(double x, double y);
-  bool isgreaterequal(long double x, long double y);
+  constexpr bool isgreaterequal(float x, float y);
+  constexpr bool isgreaterequal(double x, double y);
+  constexpr bool isgreaterequal(long double x, long double y);
 
-  bool isless(float x, float y);
-  bool isless(double x, double y);
-  bool isless(long double x, long double y);
+  constexpr bool isless(float x, float y);
+  constexpr bool isless(double x, double y);
+  constexpr bool isless(long double x, long double y);
 
-  bool islessequal(float x, float y);
-  bool islessequal(double x, double y);
-  bool islessequal(long double x, long double y);
+  constexpr bool islessequal(float x, float y);
+  constexpr bool islessequal(double x, double y);
+  constexpr bool islessequal(long double x, long double y);
 
-  bool islessgreater(float x, float y);
-  bool islessgreater(double x, double y);
-  bool islessgreater(long double x, long double y);
+  constexpr bool islessgreater(float x, float y);
+  constexpr bool islessgreater(double x, double y);
+  constexpr bool islessgreater(long double x, long double y);
 
-  bool isunordered(float x, float y);
-  bool isunordered(double x, double y);
-  bool isunordered(long double x, long double y);
+  constexpr bool isunordered(float x, float y);
+  constexpr bool isunordered(double x, double y);
+  constexpr bool isunordered(long double x, long double y);
 
   // \ref{sf.cmath}, mathematical special functions
 
@@ -10014,12 +10014,12 @@
 
 \indexlibraryglobal{abs}%
 \begin{itemdecl}
-int abs(int j);
-long int abs(long int j);
-long long int abs(long long int j);
-float abs(float j);
-double abs(double j);
-long double abs(long double j);
+constexpr int abs(int j);
+constexpr long int abs(long int j);
+constexpr long long int abs(long long int j);
+constexpr float abs(float j);
+constexpr double abs(double j);
+constexpr long double abs(long double j);
 \end{itemdecl}
 
 \begin{itemdescr}
diff --git a/source/support.tex b/source/support.tex
index e8ccd20800..cbd48c58be 100644
--- a/source/support.tex
+++ b/source/support.tex
@@ -219,21 +219,21 @@
   void srand(unsigned int seed);
 
   // \ref{c.math.abs}, absolute values
-  int abs(int j);
-  long int abs(long int j);
-  long long int abs(long long int j);
-  float abs(float j);
-  double abs(double j);
-  long double abs(long double j);
-
-  long int labs(long int j);
-  long long int llabs(long long int j);
-
-  div_t div(int numer, int denom);
-  ldiv_t div(long int numer, long int denom);                   // see \ref{library.c}
-  lldiv_t div(long long int numer, long long int denom);        // see \ref{library.c}
-  ldiv_t ldiv(long int numer, long int denom);
-  lldiv_t lldiv(long long int numer, long long int denom);
+  constexpr int abs(int j);
+  constexpr long int abs(long int j);
+  constexpr long long int abs(long long int j);
+  constexpr float abs(float j);
+  constexpr double abs(double j);
+  constexpr long double abs(long double j);
+
+  constexpr long int labs(long int j);
+  constexpr long long int llabs(long long int j);
+
+  constexpr div_t div(int numer, int denom);
+  constexpr ldiv_t div(long int numer, long int denom);                 // see \ref{library.c}
+  constexpr lldiv_t div(long long int numer, long long int denom);      // see \ref{library.c}
+  constexpr ldiv_t ldiv(long int numer, long int denom);
+  constexpr lldiv_t lldiv(long long int numer, long long int denom);
 }
 \end{codeblock}
 
@@ -589,6 +589,7 @@
 #define @\defnlibxname{cpp_lib_complex_udls}@                      201309L // also in \libheader{complex}
 #define @\defnlibxname{cpp_lib_concepts}@                          202002L // also in \libheader{concepts}
 #define @\defnlibxname{cpp_lib_constexpr_algorithms}@              201806L // also in \libheader{algorithm}
+#define @\defnlibxname{cpp_lib_constexpr_cmath}@                   202202L // also in \libheader{cmath}, \libheader{cstdlib}
 #define @\defnlibxname{cpp_lib_constexpr_complex}@                 201711L // also in \libheader{complex}
 #define @\defnlibxname{cpp_lib_constexpr_dynamic_alloc}@           201907L // also in \libheader{memory}
 #define @\defnlibxname{cpp_lib_constexpr_functional}@              201907L // also in \libheader{functional}