Assume that we have rint().

Windows has this since _MSC_VER >= 1200, and so do all other live
platforms according to the buildfarm, so remove the configure probe
and src/port/ substitution.

This is part of a series of commits to get rid of no-longer-relevant
configure checks and dead src/port/ code.  I'm committing them separately
to make it easier to back out individual changes if they prove less
portable than I expect.

Discussion: https://postgr.es/m/15379.1582221614@sss.pgh.pa.us

configure

@@ -15628,19 +15628,6 @@ esac
 
 fi
 
-ac_fn_c_check_func "$LINENO" "rint" "ac_cv_func_rint"
-if test "x$ac_cv_func_rint" = xyes; then :
-  $as_echo "#define HAVE_RINT 1" >>confdefs.h
-
-else
-  case " $LIBOBJS " in
-  *" rint.$ac_objext "* ) ;;
-  *) LIBOBJS="$LIBOBJS rint.$ac_objext"
- ;;
-esac
-
-fi
-
 ac_fn_c_check_func "$LINENO" "srandom" "ac_cv_func_srandom"
 if test "x$ac_cv_func_srandom" = xyes; then :
   $as_echo "#define HAVE_SRANDOM 1" >>confdefs.h

configure.in

@@ -1707,7 +1707,6 @@ AC_REPLACE_FUNCS(m4_normalize([
 	pread
 	pwrite
 	random
-	rint
 	srandom
 	strlcat
 	strlcpy

src/include/pg_config.h.in

@@ -451,9 +451,6 @@
 /* Define to 1 if you have the `readlink' function. */
 #undef HAVE_READLINK
 
-/* Define to 1 if you have the `rint' function. */
-#undef HAVE_RINT
-
 /* Define to 1 if you have the global variable
    'rl_completion_append_character'. */
 #undef HAVE_RL_COMPLETION_APPEND_CHARACTER

src/include/port.h

@@ -385,10 +385,6 @@ extern float pg_strtof(const char *nptr, char **endptr);
 extern char *mkdtemp(char *path);
 #endif
 
-#ifndef HAVE_RINT
-extern double rint(double x);
-#endif
-
 #ifndef HAVE_INET_ATON
 #include <netinet/in.h>
 #include <arpa/inet.h>

src/port/rint.c

@@ -1,97 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * rint.c
- *	  rint() implementation
- *
- * By Pedro Gimeno Fortea, donated to the public domain
- *
- * IDENTIFICATION
- *	  src/port/rint.c
- *
- *-------------------------------------------------------------------------
- */
-#include "c.h"
-
-#include <math.h>
-
-/*
- * Round to nearest integer, with halfway cases going to the nearest even.
- */
-double
-rint(double x)
-{
-	double		x_orig;
-	double		r;
-
-	/* Per POSIX, NaNs must be returned unchanged. */
-	if (isnan(x))
-		return x;
-
-	if (x <= 0.0)
-	{
-		/* Both positive and negative zero should be returned unchanged. */
-		if (x == 0.0)
-			return x;
-
-		/*
-		 * Subtracting 0.5 from a number very close to -0.5 can round to
-		 * exactly -1.0, producing incorrect results, so we take the opposite
-		 * approach: add 0.5 to the negative number, so that it goes closer to
-		 * zero (or at most to +0.5, which is dealt with next), avoiding the
-		 * precision issue.
-		 */
-		x_orig = x;
-		x += 0.5;
-
-		/*
-		 * Be careful to return minus zero when input+0.5 >= 0, as that's what
-		 * rint() should return with negative input.
-		 */
-		if (x >= 0.0)
-			return -0.0;
-
-		/*
-		 * For very big numbers the input may have no decimals.  That case is
-		 * detected by testing x+0.5 == x+1.0; if that happens, the input is
-		 * returned unchanged.  This also covers the case of minus infinity.
-		 */
-		if (x == x_orig + 1.0)
-			return x_orig;
-
-		/* Otherwise produce a rounded estimate. */
-		r = floor(x);
-
-		/*
-		 * If the rounding did not produce exactly input+0.5 then we're done.
-		 */
-		if (r != x)
-			return r;
-
-		/*
-		 * The original fractional part was exactly 0.5 (since
-		 * floor(input+0.5) == input+0.5).  We need to round to nearest even.
-		 * Dividing input+0.5 by 2, taking the floor and multiplying by 2
-		 * yields the closest even number.  This part assumes that division by
-		 * 2 is exact, which should be OK because underflow is impossible
-		 * here: x is an integer.
-		 */
-		return floor(x * 0.5) * 2.0;
-	}
-	else
-	{
-		/*
-		 * The positive case is similar but with signs inverted and using
-		 * ceil() instead of floor().
-		 */
-		x_orig = x;
-		x -= 0.5;
-		if (x <= 0.0)
-			return 0.0;
-		if (x == x_orig - 1.0)
-			return x_orig;
-		r = ceil(x);
-		if (r != x)
-			return r;
-		return ceil(x * 0.5) * 2.0;
-	}
-}

src/tools/msvc/Mkvcbuild.pm

@@ -104,8 +104,6 @@ sub mkvcbuild
 	  sprompt.c strerror.c tar.c thread.c
 	  win32env.c win32error.c win32security.c win32setlocale.c);
 
-	push(@pgportfiles, 'rint.c') if ($vsVersion < '12.00');
-
 	push(@pgportfiles, 'strtof.c') if ($vsVersion < '14.00');
 
 	if ($vsVersion >= '9.00')

src/tools/msvc/Solution.pm

@@ -321,7 +321,6 @@ sub GenerateFiles
 		HAVE_READLINE_HISTORY_H     => undef,
 		HAVE_READLINE_READLINE_H    => undef,
 		HAVE_READLINK               => undef,
-		HAVE_RINT                   => 1,
 		HAVE_RL_COMPLETION_APPEND_CHARACTER      => undef,
 		HAVE_RL_COMPLETION_MATCHES               => undef,
 		HAVE_RL_COMPLETION_SUPPRESS_QUOTE        => undef,