openbsd: ensure we link to the built libperl.a, not the system libperl.a

embed.fnc

@@ -663,6 +663,10 @@ Adp	|SV *	|amagic_deref_call					\
 p	|bool	|amagic_is_enabled					\
 				|int method
 
+CTdp	|void	|api_version_assert					\
+				|size_t interp_size			\
+				|NULLOK void *v_my_perl 		\
+				|NN const char *api_version
 ETXip	|void	|append_utf8_from_native_byte				\
 				|const U8 byte				\
 				|NN U8 **dest

embed.h

@@ -128,6 +128,7 @@
 # define _to_utf8_upper_flags(a,b,c,d,e)        Perl__to_utf8_upper_flags(aTHX_ a,b,c,d,e)
 # define amagic_call(a,b,c,d)                   Perl_amagic_call(aTHX_ a,b,c,d)
 # define amagic_deref_call(a,b)                 Perl_amagic_deref_call(aTHX_ a,b)
+# define api_version_assert                     Perl_api_version_assert
 # define apply_attrs_string(a,b,c,d)            Perl_apply_attrs_string(aTHX_ a,b,c,d)
 # define apply_builtin_cv_attributes(a,b)       Perl_apply_builtin_cv_attributes(aTHX_ a,b)
 # define atfork_lock                            Perl_atfork_lock

lib/ExtUtils/t/Embed.t

@@ -103,13 +103,26 @@ if ($^O eq 'VMS') {
    elsif ($^O eq 'os390' && $Config{usedl}) {
     push(@cmd,"-L$lib", ldopts());
    } else { # Not MSWin32 or OS/390 (z/OS) dynamic.
-    push(@cmd,"-L$lib",'-lperl');
+    my $ldopts = ldopts();
+    if ($^O eq 'openbsd' && $Config{useshrplib} eq "false") {
+        # see github #22125
+        # with OpenBSD, the packaged gcc (tries to) link
+        # against the system libperl, this will be fine once
+        # this perl gets installed, but that's not so good when
+        # testing against the uninstalled perl.
+        # This also matches how Makefile.SH links the perl executable
+        push @cmd, "$lib/libperl.a";
+        $ldopts =~ s/ -lperl\b//;
+    }
+    else {
+        push(@cmd,"-L$lib",'-lperl');
+    }
     local $SIG{__WARN__} = sub {
 	warn $_[0] unless $_[0] =~ /No library found for .*perl/
     };
     push(@cmd, '-Zlinker', '/PM:VIO')	# Otherwise puts a warning to STDOUT!
 	if $^O eq 'os2' and $Config{ldflags} =~ /(?<!\S)-Zomf\b/;
-    push(@cmd,ldopts());
+    push(@cmd, $ldopts);
    }
 
    if ($^O eq 'aix') { # AIX needs an explicit symbol export list.
@@ -196,6 +209,8 @@ int main(int argc, char **argv, char **env) {
     perl_construct(my_perl);
     PL_exit_flags |= PERL_EXIT_WARN;
 
+    PERL_API_VERSION_ASSERT;
+
     my_puts("ok 3");
 
     perl_parse(my_perl, NULL, (sizeof(cmds)/sizeof(char *))-1, (char **)cmds, env);

perl.h

@@ -9264,6 +9264,14 @@ END_EXTERN_C
 #  define PERL_STACK_REALIGN
 #endif
 
+#ifdef MULTIPLICITY
+#  define PERL_API_VERSION_ASSERT \
+  Perl_api_version_assert(sizeof(PerlInterpreter), aTHX, PERL_API_VERSION_STRING)
+#else
+#  define PERL_API_VERSION_ASSERT \
+  Perl_api_version_assert(sizeof(PerlInterpreter), NULL, PERL_API_VERSION_STRING)
+#endif
+
 /*
 
    (KEEP THIS LAST IN perl.h!)

pod/perldelta.pod

@@ -289,7 +289,8 @@ made:
 
 =item *
 
-XXX
+When testing embedding, add a sanity check to ensure the C<libperl> we
+link against matches the perl we are building.  [GH #22125]
 
 =back
 
@@ -338,9 +339,10 @@ L</Modules and Pragmata> section.
 
 =over 4
 
-=item XXX-some-platform
+=item OpenBSD
 
-XXX
+When testing embedding, ensure we link against the correct static
+libperl. [GH #22125]
 
 =back
 

pod/perldiag.pod

@@ -4020,6 +4020,11 @@ See L</500 Server error>.
 by a missing delimiter on a string or pattern, because it eventually
 ended earlier on the current line.
 
+=item Mismatch between expected and libperl %s
+
+(F) For an embedded perl, the perl headers and configuration you built
+your binary against don't match the library you've linked with.
+
 =item Mismatched brackets in template
 
 (F) A pack template could not be parsed because pairs of C<[...]> or

util.c

@@ -5737,6 +5737,52 @@ S_xs_version_bootcheck(pTHX_ SSize_t items, SSize_t ax, const char *xs_p,
     }
 }
 
+/*
+=for apidoc api_version_assert
+
+Used by the PERL_API_VERSION_CHECK macro to compare the perl the
+object was built with and the perl that C<libperl> was built with.
+
+This can be used to ensure that these match and produces a more
+diagnosable than random crashes and mis-behaviour.
+
+=cut
+*/
+
+void
+Perl_api_version_assert(size_t interp_size, void *v_my_perl,
+                        const char *api_version) {
+    dTHX;
+
+    PERL_ARGS_ASSERT_API_VERSION_ASSERT;
+
+    if (interp_size != sizeof(PerlInterpreter)) {
+        /* detects various types of configuration mismatches */
+        /* diag_listed_as: Mismatch between expected and libperl %s */
+        Perl_croak(aTHX_
+                   "Mismatch between expected and libperl interpreter structure size %zd vs %zd",
+                   interp_size, sizeof(PerlInterpreter));
+    }
+    if (
+#ifdef MULTIPLICITY
+      v_my_perl != my_perl
+#else
+      v_my_perl != NULL
+#endif
+        ) {
+        /* detect threads vs non-threads mismatch */
+        /* diag_listed_as: Mismatch between expected and libperl %s */
+        Perl_croak(aTHX_
+                   "Mismatch between expected and libperl interpreter pointer");
+    }
+    if (strNE(api_version, PERL_API_VERSION_STRING)) {
+        /* diag_listed_as: Mismatch between expected and libperl %s */
+        Perl_croak(aTHX_
+                   "Mismatch between expected and libperl API versions %s vs %s",
+                   api_version, PERL_API_VERSION_STRING);
+    }
+}
+
 PERL_STATIC_INLINE bool
 S_gv_has_usable_name(pTHX_ GV *gv)
 {