add API to test that libperl and the current executable are compatible

Issue #22125 detected that we weren't linking the correct library with
the embedded test with gcc on OpenBSD, so add an API to perform a
sanity check by comparing the size of the perl interpreter
structure (or its size if it was a structure) and expected perl API
version between those seen in the binary and those compiled into
libperl.

Author: tonycoz

embed.fnc

@@ -686,6 +686,10 @@ Adp	|SV *	|amagic_deref_call					\
 p	|bool	|amagic_is_enabled					\
 				|int method
 
+EMTp	|void	|api_version_check					\
+				|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

lib/ExtUtils/t/Embed.t

@@ -158,7 +158,7 @@ $embed_test = "run/nodebug $exe" if $^O eq 'VMS';
 print "# embed_test = $embed_test\n";
 $status = system($embed_test);
 print (($status? 'not ':'')."ok 10 # system returned $status\n");
-unlink($exe,"embed_test.c",$obj);
+#unlink($exe,"embed_test.c",$obj);
 unlink("$exe.manifest") if $cl and $Config{'ccversion'} =~ /^(\d+)/ and $1 >= 14;
 unlink("$exe$Config{exe_ext}") if $skip_exe;
 unlink("embed_test.map","embed_test.lis") if $^O eq 'VMS';
@@ -196,6 +196,8 @@ int main(int argc, char **argv, char **env) {
     perl_construct(my_perl);
     PL_exit_flags |= PERL_EXIT_WARN;
 
+    PERL_API_VERSION_CHECK;
+
     my_puts("ok 3");
 
     perl_parse(my_perl, NULL, (sizeof(cmds)/sizeof(char *))-1, (char **)cmds, env);

perl.h

@@ -9265,6 +9265,14 @@ END_EXTERN_C
 #  define PERL_STACK_REALIGN
 #endif
 
+#ifdef MULTIPLICITY
+#  define PERL_API_VERSION_CHECK \
+  Perl_api_version_check(sizeof(PerlInterpreter), aTHX, PERL_API_VERSION_STRING)
+#else
+#  define PERL_API_VERSION_CHECK \
+  Perl_api_version_check(sizeof(PerlInterpreter), NULL, PERL_API_VERSION_STRING)
+#endif
+
 /*
 
    (KEEP THIS LAST IN perl.h!)

pod/perldiag.pod

@@ -4024,6 +4024,11 @@ 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

proto.h

@@ -5686,6 +5686,52 @@ S_xs_version_bootcheck(pTHX_ SSize_t items, SSize_t ax, const char *xs_p,
     }
 }
 
+/*
+=for apidoc api_version_check
+
+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_check(size_t interp_size, void *v_my_perl,
+                       const char *api_version) {
+    dTHX;
+
+    PERL_ARGS_ASSERT_API_VERSION_CHECK;
+
+    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)
 {