Move config check to compile time. Support assume. (#805)

Add support for `[[assume(...)]]`.

Streamline some feature checks: ones that don't affect ABI can still happen at compile time, speeding up configure.

NEWS

@@ -1,4 +1,6 @@
 7.9.1
+ - Move `[[likely]]` feature check back to compile time, to speed up configure.
+ - Support `[[assume(...)]]`.
 7.9.0
  - Support standard libraries without `std::basic_string<std::byte>` etc.
  - `std::basic_string<std::byte` becomes `pqxx::bytes`. (#726)

cmake/pqxx_cxx_feature_checks.cmake

@@ -71,10 +71,6 @@ try_compile(
     PQXX_HAVE_THREAD_LOCAL ${PROJECT_BINARY_DIR}
     SOURCES ${PROJECT_SOURCE_DIR}/config-tests/PQXX_HAVE_THREAD_LOCAL.cxx
 )
-try_compile(
-    PQXX_HAVE_UNREACHABLE ${PROJECT_BINARY_DIR}
-    SOURCES ${PROJECT_SOURCE_DIR}/config-tests/PQXX_HAVE_UNREACHABLE.cxx
-)
 try_compile(
     PQXX_HAVE_YEAR_MONTH_DAY ${PROJECT_BINARY_DIR}
     SOURCES ${PROJECT_SOURCE_DIR}/config-tests/PQXX_HAVE_YEAR_MONTH_DAY.cxx

config/Makefile.in

@@ -124,7 +124,7 @@ am__can_run_installinfo = \
   esac
 am__tagged_files = $(HEADERS) $(SOURCES) $(TAGS_FILES) $(LISP)
 am__DIST_COMMON = $(srcdir)/Makefile.in compile config.guess \
-	config.sub depcomp install-sh ltmain.sh missing mkinstalldirs
+	config.sub install-sh ltmain.sh missing mkinstalldirs
 DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)
 ACLOCAL = @ACLOCAL@
 AMTAR = @AMTAR@

configitems

@@ -22,6 +22,5 @@ PQXX_HAVE_SSIZE	public	compiler
 PQXX_HAVE_STRERROR_R	public	compiler
 PQXX_HAVE_STRERROR_S	public	compiler
 PQXX_HAVE_THREAD_LOCAL       internal        compiler
-PQXX_HAVE_UNREACHABLE	public	compiler
 PQXX_HAVE_YEAR_MONTH_DAY	public	compiler
 VERSION	internal	autotools

configure

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.71 for libpqxx 7.9.0.
+# Generated by GNU Autoconf 2.71 for libpqxx 7.9.1.
 #
 # Report bugs to <Jeroen T. Vermeulen>.
 #
@@ -621,8 +621,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='libpqxx'
 PACKAGE_TARNAME='libpqxx'
-PACKAGE_VERSION='7.9.0'
-PACKAGE_STRING='libpqxx 7.9.0'
+PACKAGE_VERSION='7.9.1'
+PACKAGE_STRING='libpqxx 7.9.1'
 PACKAGE_BUGREPORT='Jeroen T. Vermeulen'
 PACKAGE_URL=''
 
@@ -1385,7 +1385,7 @@ 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 7.9.0 to adapt to many kinds of systems.
+\`configure' configures libpqxx 7.9.1 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1456,7 +1456,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of libpqxx 7.9.0:";;
+     short | recursive ) echo "Configuration of libpqxx 7.9.1:";;
    esac
   cat <<\_ACEOF
 
@@ -1582,7 +1582,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-libpqxx configure 7.9.0
+libpqxx configure 7.9.1
 generated by GNU Autoconf 2.71
 
 Copyright (C) 2021 Free Software Foundation, Inc.
@@ -1957,7 +1957,7 @@ 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 7.9.0, which was
+It was created by libpqxx $as_me 7.9.1, which was
 generated by GNU Autoconf 2.71.  Invocation command line was
 
   $ $0$ac_configure_args_raw
@@ -3452,7 +3452,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='libpqxx'
- VERSION='7.9.0'
+ VERSION='7.9.1'
 
 
 printf "%s\n" "#define PACKAGE \"$PACKAGE\"" >>confdefs.h
@@ -4108,11 +4108,11 @@ if test x$ac_prog_cxx_stdcxx = xno
 then :
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $CXX option to enable C++11 features" >&5
 printf %s "checking for $CXX option to enable C++11 features... " >&6; }
-if test ${ac_cv_prog_cxx_11+y}
+if test ${ac_cv_prog_cxx_cxx11+y}
 then :
   printf %s "(cached) " >&6
 else $as_nop
-  ac_cv_prog_cxx_11=no
+  ac_cv_prog_cxx_cxx11=no
 ac_save_CXX=$CXX
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
@@ -4154,11 +4154,11 @@ if test x$ac_prog_cxx_stdcxx = xno
 then :
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $CXX option to enable C++98 features" >&5
 printf %s "checking for $CXX option to enable C++98 features... " >&6; }
-if test ${ac_cv_prog_cxx_98+y}
+if test ${ac_cv_prog_cxx_cxx98+y}
 then :
   printf %s "(cached) " >&6
 else $as_nop
-  ac_cv_prog_cxx_98=no
+  ac_cv_prog_cxx_cxx98=no
 ac_save_CXX=$CXX
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
@@ -18264,46 +18264,6 @@ fi
 rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $PQXX_HAVE_THREAD_LOCAL" >&5
 printf "%s\n" "$PQXX_HAVE_THREAD_LOCAL" >&6; }
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking PQXX_HAVE_UNREACHABLE" >&5
-printf %s "checking PQXX_HAVE_UNREACHABLE... " >&6; }
-PQXX_HAVE_UNREACHABLE=yes
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-// Feature check for 'PQXX_HAVE_UNREACHABLE'.
-
-// Generated by generate_cxx_checks.py.
-
-#include <version>
-
-#if !defined(__cpp_lib_unreachable)
-
-#  error "No PQXX_HAVE_UNREACHABLE: __cpp_lib_unreachable is not set."
-
-#endif
-
-#if !__cpp_lib_unreachable
-
-#  error "No PQXX_HAVE_UNREACHABLE: __cpp_lib_unreachable is false."
-
-#endif
-
-
-
-int main() {}
-
-
-_ACEOF
-if ac_fn_cxx_try_compile "$LINENO"
-then :
-
-printf "%s\n" "#define PQXX_HAVE_UNREACHABLE 1" >>confdefs.h
-
-else $as_nop
-  PQXX_HAVE_UNREACHABLE=no
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
-{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $PQXX_HAVE_UNREACHABLE" >&5
-printf "%s\n" "$PQXX_HAVE_UNREACHABLE" >&6; }
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking PQXX_HAVE_YEAR_MONTH_DAY" >&5
 printf %s "checking PQXX_HAVE_YEAR_MONTH_DAY... " >&6; }
 PQXX_HAVE_YEAR_MONTH_DAY=yes
@@ -19546,7 +19506,7 @@ cat >>$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 7.9.0, which was
+This file was extended by libpqxx $as_me 7.9.1, which was
 generated by GNU Autoconf 2.71.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -19614,7 +19574,7 @@ ac_cs_config_escaped=`printf "%s\n" "$ac_cs_config" | sed "s/^ //; s/'/'\\\\\\\\
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config='$ac_cs_config_escaped'
 ac_cs_version="\\
-libpqxx config.status 7.9.0
+libpqxx config.status 7.9.1
 configured by $0, generated by GNU Autoconf 2.71,
   with options \\"\$ac_cs_config\\"
 

cxx_features.txt

@@ -17,4 +17,3 @@ PQXX_HAVE_MULTIDIM __cpp_multidimensional_subscript
 PQXX_HAVE_SOURCE_LOCATION __cpp_lib_source_location
 PQXX_HAVE_SPAN __cpp_lib_span
 PQXX_HAVE_SSIZE __cpp_lib_ssize
-PQXX_HAVE_UNREACHABLE __cpp_lib_unreachable

include/pqxx/array.hxx

@@ -218,6 +218,7 @@ private:
     case group::SJIS: parse<group::SJIS>(data); break;
     case group::UHC: parse<group::UHC>(data); break;
     case group::UTF8: parse<group::UTF8>(data); break;
+    default: PQXX_UNREACHABLE; break;
     }
   }
 
@@ -301,14 +302,12 @@ private:
     std::size_t dim{outer};
 
     // Extent counters, one per "real" dimension.
-    // Note initialiser syntax; this should zero-initialise all elements.
+    // Note initialiser syntax; this zero-initialises all elements.
     std::array<std::size_t, DIMENSIONS> extents{};
-#if !defined(NDEBUG)
-    for (auto const e : extents) assert(e == 0u);
-#endif
 
     // Current parsing position.
     std::size_t here{0};
+    PQXX_ASSUME(here <= sz);
     while (here < sz)
     {
       if (data[here] == '{')
@@ -321,6 +320,7 @@ private:
               "Array text representation closed and reopened its outside "
               "brace pair."};
           assert(here == 0);
+          PQXX_ASSUME(here == 0);
         }
         else
         {
@@ -412,13 +412,15 @@ private:
         }
         }
         here = end;
+        PQXX_ASSUME(here <= sz);
         here = parse_field_end(data, here);
       }
     }
 
     if (dim != outer)
       throw conversion_error{"Malformed array; may be truncated."};
     assert(know_extents_from == 0);
+    PQXX_ASSUME(know_extents_from == 0);
 
     init_factors();
   }

include/pqxx/config.h.in

@@ -111,9 +111,6 @@
 /* Define if this feature is available. */
 #undef PQXX_HAVE_THREAD_LOCAL
 
-/* Define if this feature is available. */
-#undef PQXX_HAVE_UNREACHABLE
-
 /* Define if this feature is available. */
 #undef PQXX_HAVE_YEAR_MONTH_DAY
 

include/pqxx/doc/mainpage.md

@@ -1,7 +1,7 @@
 libpqxx                                      {#mainpage}
 =======
 
-@version 7.9.0
+@version 7.9.1
 @author Jeroen T. Vermeulen
 @see http://pqxx.org
 @see https://github.com/jtv/libpqxx

include/pqxx/field.hxx

@@ -260,12 +260,13 @@ public:
    * @param c Column number of this field.
    */
   [[deprecated(
-    "Do not construct fields yourself.  Get them from the row.")]] field(row const &r, row_size_type c) noexcept;
+    "Do not construct fields yourself.  Get them from the row.")]]
+  field(row const &r, row_size_type c) noexcept;
 
   /// Constructor.  Do not call this yourself; libpqxx will do it for you.
   [[deprecated(
-    "Do not construct fields yourself.  Get them from the "
-    "row.")]] field() noexcept = default;
+    "Do not construct fields yourself.  Get them from the row.")]]
+  field() noexcept = default;
 
 
 protected:

include/pqxx/internal/array-composite.hxx

@@ -23,9 +23,11 @@ inline std::size_t scan_double_quoted_string(
   // TODO: find_char<'"', '\\'>().
   using scanner = glyph_scanner<ENC>;
   auto next{scanner::call(input, size, pos)};
+  PQXX_ASSUME(next > pos);
   bool at_quote{false};
   pos = next;
   next = scanner::call(input, size, pos);
+  PQXX_ASSUME(next > pos);
   while (pos < size)
   {
     if (at_quote)
@@ -51,6 +53,7 @@ inline std::size_t scan_double_quoted_string(
         // Backslash escape.  Skip ahead by one more character.
         pos = next;
         next = scanner::call(input, size, pos);
+        PQXX_ASSUME(next > pos);
         break;
 
       case '"':
@@ -66,6 +69,7 @@ inline std::size_t scan_double_quoted_string(
     }
     pos = next;
     next = scanner::call(input, size, pos);
+    PQXX_ASSUME(next > pos);
   }
   if (not at_quote)
     throw argument_error{
@@ -90,6 +94,8 @@ inline std::string parse_double_quoted_string(
   using scanner = glyph_scanner<ENC>;
   auto here{scanner::call(input, end, pos)},
     next{scanner::call(input, end, here)};
+  PQXX_ASSUME(here > pos);
+  PQXX_ASSUME(next > here);
   while (here < end - 1)
   {
     // A backslash here is always an escape.  So is a double-quote, since we're
@@ -101,10 +107,12 @@ inline std::string parse_double_quoted_string(
       // Skip escape.
       here = next;
       next = scanner::call(input, end, here);
+      PQXX_ASSUME(next > here);
     }
     output.append(input + here, input + next);
     here = next;
     next = scanner::call(input, end, here);
+    PQXX_ASSUME(next > here);
   }
   return output;
 }
@@ -124,10 +132,12 @@ scan_unquoted_string(char const input[], std::size_t size, std::size_t pos)
 {
   using scanner = glyph_scanner<ENC>;
   auto next{scanner::call(input, size, pos)};
+  PQXX_ASSUME(next > pos);
   while ((pos < size) and ((next - pos) > 1 or ((input[pos] != STOP) and ...)))
   {
     pos = next;
     next = scanner::call(input, size, pos);
+    PQXX_ASSUME(next > pos);
   }
   return pos;
 }
@@ -174,6 +184,7 @@ inline void parse_composite_field(
 {
   assert(index <= last_field);
   auto next{glyph_scanner<ENC>::call(std::data(input), std::size(input), pos)};
+  PQXX_ASSUME(next > pos);
   if ((next - pos) != 1)
     throw conversion_error{"Non-ASCII character in composite-type syntax."};
 
@@ -195,6 +206,7 @@ inline void parse_composite_field(
   case '"': {
     auto const stop{
       scan_double_quoted_string<ENC>(std::data(input), std::size(input), pos)};
+    PQXX_ASSUME(stop > pos);
     auto const text{
       parse_double_quoted_string<ENC>(std::data(input), stop, pos)};
     field = from_string<T>(text);
@@ -205,6 +217,7 @@ inline void parse_composite_field(
   default: {
     auto const stop{scan_unquoted_string<ENC, ',', ')', ']'>(
       std::data(input), std::size(input), pos)};
+    PQXX_ASSUME(stop >= pos);
     field =
       from_string<T>(std::string_view{std::data(input) + pos, stop - pos});
     pos = stop;
@@ -214,6 +227,7 @@ inline void parse_composite_field(
 
   // Expect a comma or a closing parenthesis.
   next = glyph_scanner<ENC>::call(std::data(input), std::size(input), pos);
+  PQXX_ASSUME(next > pos);
 
   if ((next - pos) != 1)
     throw conversion_error{

include/pqxx/internal/concat.hxx

@@ -12,7 +12,9 @@ namespace pqxx::internal
 template<typename TYPE>
 void render_item(TYPE const &item, char *&here, char *end)
 {
-  here = string_traits<TYPE>::into_buf(here, end, item) - 1;
+  auto const next = string_traits<TYPE>::into_buf(here, end, item) - 1;
+  PQXX_ASSUME(next >= here);
+  here = next;
 }