1 files changed, 24 insertions, 0 deletions
diff --git a/languages/cpp/app_templates/prc-tool/callback.h b/languages/cpp/app_templates/prc-tool/callback.h
new file mode 100644
index 00000000..bf0ead45
--- /dev/null
+++ b/languages/cpp/app_templates/prc-tool/callback.h
@@ -0,0 +1,24 @@
+#ifndef __CALLBACK_H__
+#define __CALLBACK_H__
+
+/* This is a workaround for a bug in the current version of gcc:
+
+   gcc assumes that no one will touch %a4 after it is set up in crt0.o.
+   This isn't true if a function is called as a callback by something
+   that wasn't compiled by gcc (like FrmCloseAllForms()).  It may also
+   not be true if it is used as a callback by something in a different
+   shared library.
+
+   We really want a function attribute "callback" which will insert this
+   progloue and epilogoue automatically.
+   
+      - Ian */
+
+register void *reg_a4 asm("%a4");
+
+#define CALLBACK_PROLOGUE \
+    void *save_a4 = reg_a4; asm("move.l %%a5,%%a4; sub.l #edata,%%a4" : :);
+
+#define CALLBACK_EPILOGUE reg_a4 = save_a4;
+
+#endif