MSVC: Test whether 32-bit Perl needs -D_USE_32BIT_TIME_T.

Commits 5a5c2feca3fd858e70ea348822595547e6fa6c15 and
b5178c5d08ca59e30f9d9428fa6fdb2741794e65 introduced support for modern
MSVC-built, 32-bit Perl, but they broke use of MinGW-built, 32-bit Perl
distributions like Strawberry Perl and modern ActivePerl.  Perl has no
robust means to report whether it expects a -D_USE_32BIT_TIME_T ABI, so
test this.  Back-patch to 9.3 (all supported versions).

The chief alternative was a heuristic of adding -D_USE_32BIT_TIME_T when
$Config{gccversion} is nonempty.  That banks on every gcc-built Perl
using the same ABI.  gcc could change its default ABI the way MSVC once
did, and one could build Perl with gcc and the non-default ABI.

The GNU make build system could benefit from a similar test, without
which it does not support MSVC-built Perl.  For now, just add a comment.
Most users taking the special step of building Perl with MSVC probably
build PostgreSQL with MSVC.

Discussion: https://postgr.es/m/20171130041441.GA3161526@rfd.leadboat.com

diff --git a/config/perl.m4 b/config/perl.m4
index 76b1a92e3a00f57c31f43429beee960f6ea74bd0..caefb0705e794674a55b771736cd25c9bf1e864c 100644 (file)
--- a/config/perl.m4
+++ b/config/perl.m4
@@ -48,19 +48,23 @@ AC_DEFUN([PGAC_CHECK_PERL_CONFIGS],
 
 # PGAC_CHECK_PERL_EMBED_CCFLAGS
 # -----------------------------
-# We selectively extract stuff from $Config{ccflags}.  We don't really need
-# anything except -D switches, and other sorts of compiler switches can
-# actively break things if Perl was compiled with a different compiler.
-# Moreover, although Perl likes to put stuff like -D_LARGEFILE_SOURCE and
-# -D_FILE_OFFSET_BITS=64 here, it would be fatal to try to compile PL/Perl
-# to a different libc ABI than core Postgres uses.  The available information
-# says that all the symbols that affect Perl's own ABI begin with letters,
-# so it should be sufficient to adopt -D switches for symbols not beginning
-# with underscore.  An exception is that we need to let through
-# -D_USE_32BIT_TIME_T if it's present.  (We probably could restrict that to
-# only get through on Windows, but for the moment we let it through always.)
-# For debugging purposes, let's have the configure output report the raw
-# ccflags value as well as the set of flags we chose to adopt.
+# We selectively extract stuff from $Config{ccflags}.  For debugging purposes,
+# let's have the configure output report the raw ccflags value as well as the
+# set of flags we chose to adopt.  We don't really need anything except -D
+# switches, and other sorts of compiler switches can actively break things if
+# Perl was compiled with a different compiler.  Moreover, although Perl likes
+# to put stuff like -D_LARGEFILE_SOURCE and -D_FILE_OFFSET_BITS=64 here, it
+# would be fatal to try to compile PL/Perl to a different libc ABI than core
+# Postgres uses.  The available information says that most symbols that affect
+# Perl's own ABI begin with letters, so it's almost sufficient to adopt -D
+# switches for symbols not beginning with underscore.  Some exceptions are the
+# Windows-specific -D_USE_32BIT_TIME_T and -D__MINGW_USE_VC2005_COMPAT; see
+# Mkvcbuild.pm for details.  We absorb the former when Perl reports it.  Perl
+# never reports the latter, and we don't attempt to deduce when it's needed.
+# Consequently, we don't support using MinGW to link to MSVC-built Perl.  As
+# of 2017, all supported ActivePerl and Strawberry Perl are MinGW-built.  If
+# that changes or an MSVC-built Perl distribution becomes prominent, we can
+# revisit this limitation.
 AC_DEFUN([PGAC_CHECK_PERL_EMBED_CCFLAGS],
 [AC_REQUIRE([PGAC_PATH_PERL])
 AC_MSG_CHECKING([for CFLAGS recommended by Perl])

diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 4c2e12e22894ea490f7cea0fc17ea3719c10b239..93f364a9f2184fcfe8f646711730a7f3d8cf53aa 100644 (file)
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -28,6 +28,7 @@ my $libpgcommon;
 my $libpgfeutils;
 my $postgres;
 my $libpq;
+my @unlink_on_exit;
 
 # Set of variables for modules in contrib/ and src/test/modules/
 my $contrib_defines = { 'refint' => 'REFINT_VERBOSE' };
@@ -517,34 +518,154 @@ sub mkvcbuild
        my $plperl =
          $solution->AddProject('plperl', 'dll', 'PLs', 'src/pl/plperl');
        $plperl->AddIncludeDir($solution->{options}->{perl} . '/lib/CORE');
+       $plperl->AddReference($postgres);
+
+       my $perl_path = $solution->{options}->{perl} . '\lib\CORE\*perl*';
+
+       # ActivePerl 5.16 provided perl516.lib; 5.18 provided libperl518.a
+       my @perl_libs =
+         grep { /perl\d+\.lib$|libperl\d+\.a$/ } glob($perl_path);
+       if (@perl_libs == 1)
+       {
+           $plperl->AddLibrary($perl_libs[0]);
+       }
+       else
+       {
+           die
+"could not identify perl library version matching pattern $perl_path\n";
+       }
 
        # Add defines from Perl's ccflags; see PGAC_CHECK_PERL_EMBED_CCFLAGS
        my @perl_embed_ccflags;
        foreach my $f (split(" ", $Config{ccflags}))
        {
-           if (   $f =~ /^-D[^_]/
-               || $f =~ /^-D_USE_32BIT_TIME_T/)
+           if ($f =~ /^-D[^_]/)
            {
                $f =~ s/\-D//;
                push(@perl_embed_ccflags, $f);
            }
        }
 
-       # Perl versions before 5.13.4 don't provide -D_USE_32BIT_TIME_T
-       # regardless of how they were built.  On 32-bit Windows, assume
-       # such a version was built with a pre-MSVC-2005 compiler, and
-       # define the symbol anyway, so that we are compatible if we're
-       # being built with a later MSVC version.
-       push(@perl_embed_ccflags, '_USE_32BIT_TIME_T')
-         if $solution->{platform} eq 'Win32'
-             && $Config{PERL_REVISION} == 5
-             && ($Config{PERL_VERSION} < 13
-                 || (   $Config{PERL_VERSION} == 13
-                     && $Config{PERL_SUBVERSION} < 4));
-
-       # Also, a hack to prevent duplicate definitions of uid_t/gid_t
+       # hack to prevent duplicate definitions of uid_t/gid_t
        push(@perl_embed_ccflags, 'PLPERL_HAVE_UID_GID');
 
+       # Windows offers several 32-bit ABIs.  Perl is sensitive to
+       # sizeof(time_t), one of the ABI dimensions.  To get 32-bit time_t,
+       # use "cl -D_USE_32BIT_TIME_T" or plain "gcc".  For 64-bit time_t, use
+       # "gcc -D__MINGW_USE_VC2005_COMPAT" or plain "cl".  Before MSVC 2005,
+       # plain "cl" chose 32-bit time_t.  PostgreSQL doesn't support building
+       # with pre-MSVC-2005 compilers, but it does support linking to Perl
+       # built with such a compiler.  MSVC-built Perl 5.13.4 and later report
+       # -D_USE_32BIT_TIME_T in $Config{ccflags} if applicable, but
+       # MinGW-built Perl never reports -D_USE_32BIT_TIME_T despite typically
+       # needing it.  Ignore the $Config{ccflags} opinion about
+       # -D_USE_32BIT_TIME_T, and use a runtime test to deduce the ABI Perl
+       # expects.  Specifically, test use of PL_modglobal, which maps to a
+       # PerlInterpreter field whose position depends on sizeof(time_t).
+       if ($solution->{platform} eq 'Win32')
+       {
+           my $source_file = 'conftest.c';
+           my $obj         = 'conftest.obj';
+           my $exe         = 'conftest.exe';
+           my @conftest    = ($source_file, $obj, $exe);
+           push @unlink_on_exit, @conftest;
+           unlink $source_file;
+           open my $o, '>', $source_file
+             || croak "Could not write to $source_file";
+           print $o '
+   /* compare to plperl.h */
+   #define __inline__ __inline
+   #define PERL_NO_GET_CONTEXT
+   #include <EXTERN.h>
+   #include <perl.h>
+
+   int
+   main(int argc, char **argv)
+   {
+       int         dummy_argc = 1;
+       char       *dummy_argv[1] = {""};
+       char       *dummy_env[1] = {NULL};
+       static PerlInterpreter *interp;
+
+       PERL_SYS_INIT3(&dummy_argc, (char ***) &dummy_argv,
+                      (char ***) &dummy_env);
+       interp = perl_alloc();
+       perl_construct(interp);
+       {
+           dTHX;
+           const char  key[] = "dummy";
+
+           PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
+           hv_store(PL_modglobal, key, sizeof(key) - 1, newSViv(1), 0);
+           return hv_fetch(PL_modglobal, key, sizeof(key) - 1, 0) == NULL;
+       }
+   }
+';
+           close $o;
+
+           # Build $source_file with a given #define, and return a true value
+           # if a run of the resulting binary exits successfully.
+           my $try_define = sub {
+               my $define = shift;
+
+               unlink $obj, $exe;
+               my @cmd = (
+                   'cl',
+                   '-I' . $solution->{options}->{perl} . '/lib/CORE',
+                   (map { "-D$_" } @perl_embed_ccflags, $define || ()),
+                   $source_file,
+                   '/link',
+                   $perl_libs[0]);
+               my $compile_output = `@cmd 2>&1`;
+               -f $exe || die "Failed to build Perl test:\n$compile_output";
+
+               {
+
+                   # Some builds exhibit runtime failure through Perl warning
+                   # 'Can't spawn "conftest.exe"'; supress that.
+                   no warnings;
+
+                   # Disable error dialog boxes like we do in the postmaster.
+                   # Here, we run code that triggers relevant errors.
+                   use Win32API::File qw(SetErrorMode :SEM_);
+                   my $oldmode = SetErrorMode(
+                       SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX);
+                   system(".\\$exe");
+                   SetErrorMode($oldmode);
+               }
+
+               return !($? >> 8);
+           };
+
+           my $define_32bit_time = '_USE_32BIT_TIME_T';
+           my $ok_now            = $try_define->(undef);
+           my $ok_32bit          = $try_define->($define_32bit_time);
+           unlink @conftest;
+           if (!$ok_now && !$ok_32bit)
+           {
+
+               # Unsupported configuration.  Since we used %Config from the
+               # Perl running the build scripts, this is expected if
+               # attempting to link with some other Perl.
+               die "Perl test fails with or without -D$define_32bit_time";
+           }
+           elsif ($ok_now && $ok_32bit)
+           {
+
+               # Resulting build may work, but it's especially important to
+               # verify with "vcregress plcheck".  A refined test may avoid
+               # this outcome.
+               warn "Perl test passes with or without -D$define_32bit_time";
+           }
+           elsif ($ok_32bit)
+           {
+               push(@perl_embed_ccflags, $define_32bit_time);
+           }    # else $ok_now, hence no flag required
+       }
+
+       print "CFLAGS recommended by Perl: $Config{ccflags}\n";
+       print "CFLAGS to compile embedded Perl: ",
+         (join ' ', map { "-D$_" } @perl_embed_ccflags), "\n";
        foreach my $f (@perl_embed_ccflags)
        {
            $plperl->AddDefine($f);
@@ -614,20 +735,6 @@ sub mkvcbuild
                die 'Failed to create plperl_opmask.h' . "\n";
            }
        }
-       $plperl->AddReference($postgres);
-       my $perl_path = $solution->{options}->{perl} . '\lib\CORE\*perl*';
-       # ActivePerl 5.16 provided perl516.lib; 5.18 provided libperl518.a
-       my @perl_libs =
-         grep { /perl\d+\.lib$|libperl\d+\.a$/ } glob($perl_path);
-       if (@perl_libs == 1)
-       {
-           $plperl->AddLibrary($perl_libs[0]);
-       }
-       else
-       {
-           die
-"could not identify perl library version matching pattern $perl_path\n";
-       }
 
        # Add transform module dependent on plperl
        my $hstore_plperl = AddTransformModule(
@@ -956,4 +1063,9 @@ sub AdjustModule
    }
 }
 
+END
+{
+   unlink @unlink_on_exit;
+}
+
 1;