Re-do string conversions.

Changes some error conditions to throw `pqxx::conversion_error` instead
of `pqxx::failure` (which is more for problems closer to the actual
database, such as connection failures).

Where available, use C++17 `std::to_chars` and `std::from_chars` for
numeric conversions.  As far as I can see, these work with exactly the
right formats to communicate with postgres.  Eventually my custom code
here will go away, but for now, clang does not support these new
functions and gcc only partially.

NEWS

@@ -1,4 +1,6 @@
 6.3.2
+ - Conversion errors no longer throw pqxx::failure; always conversion_error!
+ - Use C++17's built-in numeric string conversions, if available.
  - Query numeric precision in a more sensible, standard way.
  - Avoid "dead code" warning.
 6.3.1

configitems

@@ -9,6 +9,8 @@ PACKAGE_NAME	internal	autotools
 PACKAGE_STRING	internal	autotools
 PACKAGE_TARNAME	internal	autotools
 PACKAGE_VERSION	internal	autotools
+PQXX_HAVE_CHARCONV_INT	internal	compiler
+PQXX_HAVE_CHARCONV_FLOAT	internal	compiler
 PQXX_HAVE_GCC_CONST	public	compiler
 PQXX_HAVE_GCC_DEPRECATED	public	compiler
 PQXX_HAVE_GCC_PURE	public	compiler

configure

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.69 for libpqxx 6.3.0.
+# Generated by GNU Autoconf 2.69 for libpqxx 6.3.2.
 #
 # Report bugs to <Jeroen T. Vermeulen>.
 #
@@ -590,8 +590,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='libpqxx'
 PACKAGE_TARNAME='libpqxx'
-PACKAGE_VERSION='6.3.0'
-PACKAGE_STRING='libpqxx 6.3.0'
+PACKAGE_VERSION='6.3.2'
+PACKAGE_STRING='libpqxx 6.3.2'
 PACKAGE_BUGREPORT='Jeroen T. Vermeulen'
 PACKAGE_URL=''
 
@@ -1364,7 +1364,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures libpqxx 6.3.0 to adapt to many kinds of systems.
+\`configure' configures libpqxx 6.3.2 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1435,7 +1435,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of libpqxx 6.3.0:";;
+     short | recursive ) echo "Configuration of libpqxx 6.3.2:";;
    esac
   cat <<\_ACEOF
 
@@ -1562,7 +1562,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-libpqxx configure 6.3.0
+libpqxx configure 6.3.2
 generated by GNU Autoconf 2.69
 
 Copyright (C) 2012 Free Software Foundation, Inc.
@@ -2052,7 +2052,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by libpqxx $as_me 6.3.0, which was
+It was created by libpqxx $as_me 6.3.2, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
@@ -4160,7 +4160,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='libpqxx'
- VERSION='6.3.0'
+ VERSION='6.3.2'
 
 
 cat >>confdefs.h <<_ACEOF
@@ -17581,6 +17581,87 @@ $as_echo "$have_exp_optional" >&6; }
 fi
 
 
+# It's early 2019, and gcc's charconv supports integers but not yet floats.
+# So for now, we test for int and float conversion... separately.
+#
+# It's worse for clang, which compiles the integer conversions but then fails
+# at link time because of a missing symbol "__muloti4" when compiling
+# "long long" code.  I couldn't resolve that symbol by adding -lm either.  So
+# don't just compile these tests; link them as well.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C++17 charconv integer conversion" >&5
+$as_echo_n "checking for C++17 charconv integer conversion... " >&6; }
+have_charconv_int=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <charconv>
+int
+main ()
+{
+
+			char z[100];
+			using ull = unsigned long long;
+                	auto rt = std::to_chars(z, z + sizeof(z), ull{0});
+			if (rt.ec != std::errc{}) return 1;
+			ull n;
+                	auto rf = std::from_chars(z, z + sizeof(z), n);
+			if (rf.ec != std::errc{}) return 2;
+			return int(n)
+
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+
+$as_echo "#define PQXX_HAVE_CHARCONV_INT 1" >>confdefs.h
+
+else
+  have_charconv_int=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_charconv_int" >&5
+$as_echo "$have_charconv_int" >&6; }
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C++17 charconv floating-point conversion" >&5
+$as_echo_n "checking for C++17 charconv floating-point conversion... " >&6; }
+have_charconv_float=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <charconv>
+int
+main ()
+{
+
+			char z[100];
+			using ld = long double;
+                	auto rt = std::to_chars(
+				z, z + sizeof(z), ld{0.1},
+				std::chars_format::generic);
+			if (rt.ec != std::errc{}) return 1;
+			ld n;
+                	auto rf = std::from_chars(z, z + sizeof(z), n);
+			if (rf.ec != std::errc{}) return 2;
+			return int(n)
+
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+
+$as_echo "#define PQXX_HAVE_CHARCONV_FLOAT 1" >>confdefs.h
+
+else
+  have_charconv_float=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $have_charconv_float" >&5
+$as_echo "$have_charconv_float" >&6; }
+
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for poll(2)" >&5
 $as_echo_n "checking for poll(2)... " >&6; }
   if ${ax_cv_have_poll+:} false; then :
@@ -18636,7 +18717,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by libpqxx $as_me 6.3.0, which was
+This file was extended by libpqxx $as_me 6.3.2, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -18702,7 +18783,7 @@ _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-libpqxx config.status 6.3.0
+libpqxx config.status 6.3.2
 configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 

configure.ac

@@ -252,10 +252,69 @@ AC_MSG_RESULT($have_exp_optional)
 fi
 
 
+# It's early 2019, and gcc's charconv supports integers but not yet floats.
+# So for now, we test for int and float conversion... separately.
+#
+# It's worse for clang, which compiles the integer conversions but then fails
+# at link time because of a missing symbol "__muloti4" when compiling
+# "long long" code.  I couldn't resolve that symbol by adding -lm either.  So
+# don't just compile these tests; link them as well.
+AC_MSG_CHECKING([for C++17 charconv integer conversion])
+have_charconv_int=yes
+AC_LINK_IFELSE(
+	[AC_LANG_PROGRAM(
+		[#include <charconv>],
+		[[
+			char z[100];
+			using ull = unsigned long long;
+			auto rt = std::to_chars(z, z + sizeof(z), ull{0});
+			if (rt.ec != std::errc{}) return 1;
+			ull n;
+			auto rf = std::from_chars(z, z + sizeof(z), n);
+			if (rf.ec != std::errc{}) return 2;
+			return int(n)
+		]]
+	)],
+	AC_DEFINE(
+		[PQXX_HAVE_CHARCONV_INT],
+		1,
+		[Define if <charconv> supports integer conversion.]),
+	have_charconv_int=no)
+AC_MSG_RESULT($have_charconv_int)
+
+AC_MSG_CHECKING([for C++17 charconv floating-point conversion])
+have_charconv_float=yes
+AC_LINK_IFELSE(
+	[AC_LANG_PROGRAM(
+		[#include <charconv>],
+		[[
+			char z[100];
+			using ld = long double;
+			auto rt = std::to_chars(
+				z, z + sizeof(z), ld{0.1},
+				std::chars_format::generic);
+			if (rt.ec != std::errc{}) return 1;
+			ld n;
+			auto rf = std::from_chars(z, z + sizeof(z), n);
+			if (rf.ec != std::errc{}) return 2;
+			return int(n)
+		]]
+	)],
+	AC_DEFINE(
+		[PQXX_HAVE_CHARCONV_FLOAT],
+		1,
+		[Define if <charconv> supports floating-point conversion.]),
+	have_charconv_float=no)
+AC_MSG_RESULT($have_charconv_float)
+
 AX_HAVE_POLL(
         [AX_CONFIG_FEATURE_ENABLE(poll)],
         [AX_CONFIG_FEATURE_DISABLE(poll)])
-AX_CONFIG_FEATURE([poll], [System supports poll().], [HAVE_POLL], [System supports poll().])
+AX_CONFIG_FEATURE(
+	[poll],
+	[System supports poll().],
+	[HAVE_POLL],
+	[System supports poll().])
 
 if test "$ax_cv_have_poll" != "yes"
 then

include/pqxx/config.h.in

@@ -72,6 +72,12 @@
 /* Define to the version of this package. */
 #undef PACKAGE_VERSION
 
+/* Define if <charconv> supports floating-point conversion. */
+#undef PQXX_HAVE_CHARCONV_FLOAT
+
+/* Define if <charconv> supports integer conversion. */
+#undef PQXX_HAVE_CHARCONV_INT
+
 /* Define if compiler supports [[deprecated]] attribute */
 #undef PQXX_HAVE_DEPRECATED
 

include/pqxx/version.hxx

@@ -14,7 +14,7 @@
 #include "pqxx/compiler-internal-pre.hxx"
 
 /// Full libpqxx version string.
-#define PQXX_VERSION "6.3.0"
+#define PQXX_VERSION "6.3.2"
 /// Library ABI version.
 #define PQXX_ABI "6.3"