trampoline: Fix compilation error on Linux/hppa.

* trampoline/trampoline.c (alloc_trampoline, is_trampoline): Use
'volatile' to block an invalid GCC optimization.
* callback/trampoline_r/trampoline.c (alloc_trampoline_r,
is_trampoline_r): Likewise.
* NEWS: Mention it.

ChangeLog

@@ -1,3 +1,12 @@
+2024-08-25  Bruno Haible  <[email protected]>
+
+	trampoline: Fix compilation error on Linux/hppa.
+	* trampoline/trampoline.c (alloc_trampoline, is_trampoline): Use
+	'volatile' to block an invalid GCC optimization.
+	* callback/trampoline_r/trampoline.c (alloc_trampoline_r,
+	is_trampoline_r): Likewise.
+	* NEWS: Mention it.
+
 2024-08-25  Bruno Haible  <[email protected]>
 
 	vacall: Fix build failure on Linux/hppa.

NEWS

@@ -4,6 +4,7 @@ New in 2.5:
   (Previously, a build on these platforms failed.)
   - loongarch64: Linux with lp64d ABI.
   - riscv64: Linux with musl libc.
+  - hppa: Linux.
   - powerpc: FreeBSD, NetBSD.
   - powerpc64: FreeBSD.
   - powerpc64le: FreeBSD.

callback/trampoline_r/trampoline.c

@@ -1076,8 +1076,9 @@ __TR_function alloc_trampoline_r (__TR_function address, void* data0, void* data
    *    .long   <data>
    *    .long   <address>
    */
-  { /* work around a bug in gcc 3.* */
-    void* tramp_r_address = &tramp_r;
+  { /* The 'volatile' below works around GCC bug
+       <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116481>. */
+    void* volatile tramp_r_address = &tramp_r;
     *(long *) (function + 0) = ((long *) ((char*)tramp_r_address-2))[0];
     *(long *) (function + 4) = (long) (function + 8);
     *(long *) (function + 8) = (long) data;
@@ -1728,7 +1729,9 @@ int is_trampoline_r (void* function)
 {
 #if defined(is_tramp) && defined(tramp_data)
 #ifdef __hppanew__
-  void* tramp_r_address = &tramp_r;
+  /* The 'volatile' below works around GCC bug
+     <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116481>. */
+  void* volatile tramp_r_address = &tramp_r;
   if (!(((uintptr_t)function & 3) == (TRAMP_BIAS & 3))) return 0;
 #endif
   if (is_tramp(((char*)function - TRAMP_BIAS)))

trampoline/trampoline.c

@@ -1208,8 +1208,9 @@ trampoline_function_t alloc_trampoline (trampoline_function_t address, void** va
    *    .long   <data>
    *    .long   <address>
    */
-  { /* work around a bug in gcc 3.* */
-    void* tramp_address = &tramp;
+  { /* The 'volatile' below works around GCC bug
+       <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116481>. */
+    void* volatile tramp_address = &tramp;
     *(long *) (function + 0) = ((long *) ((char*)tramp_address-2))[0];
     *(long *) (function + 4) = (long) (function + 8);
     *(long *) (function + 8) = (long) variable;
@@ -1987,7 +1988,9 @@ int is_trampoline (void* function)
 {
 #ifdef is_tramp
 #ifdef __hppanew__
-  void* tramp_address = &tramp;
+  /* The 'volatile' below works around GCC bug
+     <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116481>. */
+  void* volatile tramp_address = &tramp;
   if (!(((uintptr_t)function & 3) == (TRAMP_BIAS & 3))) return 0;
 #endif
   return ((is_tramp(((char*)function - TRAMP_BIAS))) ? 1 : 0);