jit/cache tests: Avoid test failure on hppa CPUs

[Bruno Haible]

This patch fixes a test failure on Linux/hppa and NetBSD/hppa.
The cause of the failure was that on 32-bit hppa platforms, a function pointer
is not merely a 'struct func *', but a 'struct func *' + 2.


2024-01-09  Bruno Haible  <br...@clisp.org>

        jit/cache tests: Avoid test failure on hppa CPUs.
        * tests/jit/test-cache.c (FUNCPTR_BIAS): New macro.
        (structptr_to_funcptr, funcptr_to_structptr): New functions/macros.
        (xcopy_structptr): Renamed from xcopy_funcptr. Mark as inline.
        (COPY_FUNCPTR, CODE): Use structptr_to_funcptr, funcptr_to_structptr.
        * modules/jit/cache-tests (configure.ac): Require AC_C_INLINE.

diff --git a/modules/jit/cache-tests b/modules/jit/cache-tests
index 2b30831f1d..14809b5111 100644
--- a/modules/jit/cache-tests
+++ b/modules/jit/cache-tests
@@ -22,6 +22,7 @@ gl_COMPILER_OPTION_IF([-fno-ret-protector],
   [DISABLE_OPENBSD_RETGUARD='-fno-ret-protector'],
   [DISABLE_OPENBSD_RETGUARD=])
 AC_SUBST([DISABLE_OPENBSD_RETGUARD])
+AC_REQUIRE([AC_C_INLINE])
 
 Makefile.am:
 TESTS += test-cache
diff --git a/tests/jit/test-cache.c b/tests/jit/test-cache.c
index 86fe4c7aec..76c38eec9e 100644
--- a/tests/jit/test-cache.c
+++ b/tests/jit/test-cache.c
@@ -82,6 +82,7 @@ struct func
   void *code_address;
   void *pic_base;
 };
+#  define FUNCPTR_BIAS 2
 # endif
 #else
 # define FUNCPTR_POINTS_TO_CODE
@@ -92,14 +93,32 @@ struct func
 # define CODE(funcptr) (funcptr)
 #else
 /* A function pointer points to a 'struct func'.  */
-static struct func *xcopy_funcptr (struct func *orig_funcptr)
+# if FUNCPTR_BIAS
+static inline void *
+structptr_to_funcptr (struct func *p)
+{
+  return (char *) p + FUNCPTR_BIAS;
+}
+static inline struct func *
+funcptr_to_structptr (void * volatile funcptr)
+{
+  return (struct func *) ((char *) funcptr - FUNCPTR_BIAS);
+}
+# else
+#  define structptr_to_funcptr(p) ((void *) (p))
+#  define funcptr_to_structptr(funcptr) ((struct func *) (funcptr))
+# endif
+static inline struct func *
+xcopy_structptr (struct func *structptr)
 {
   struct func *copy = (struct func *) xmalloc (sizeof (struct func));
-  *copy = *orig_funcptr;
+  *copy = *structptr;
   return copy;
 }
-# define COPY_FUNCPTR(funcptr) (void *) xcopy_funcptr ((struct func 
*)(funcptr))
-# define CODE(funcptr) (((struct func *)(funcptr))->code_address)
+# define COPY_FUNCPTR(funcptr) \
+    structptr_to_funcptr (xcopy_structptr (funcptr_to_structptr (funcptr)))
+# define CODE(funcptr) \
+    ((funcptr_to_structptr (funcptr))->code_address)
 #endif
 
 /* This test assumes that the code generated by the compiler for the