EH_ALLOC_SIZE is not large enough

[Alexandre Oliva <aoliva at redhat dot com>]

g++.old-deja/g++.eh/g+.eh/badalloc1.C fails on machines with 64-bit
pointers and longs.  The problem occurs when attempting to throw a new
exception in fn_catchthrow(), while handling the previously-thrown
integer.  The alloc_buffer in the eh_context was allocated like this:

 16 bytes (4 + padding) for the initially thrown integer
 16 bytes left unused, separating memory chunks
 80 bytes (72 + padding) for the cp_eh_info of that integer
 16 bytes left unused, separating memory chunks
 16 bytes (4 + padding) for the newly-thrown integer
 16 bytes left unused, separating memory chunks
 80 bytes (72 + padding) for the cp_eh_info of the new integer
---
240

192 is clearly not enough.

It appears to me that modifying EH_ALLOC_SIZE is an ABI change, so I'd
rather change it sooner than later.

Ok to install?

On a side note, I don't understand how the test is supposed to
accomplish what it says: it seems to attempt to check that bad_alloc
can be thrown in out-of-memory situations, but bad_alloc is never
thrown during the execution of this test.  Nathan?

Index: gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* eh-common.h (EH_ALLOC_SIZE): Bump to 240.

Index: gcc/eh-common.h
===================================================================
RCS file: /cvs/gcc/egcs/gcc/eh-common.h,v
retrieving revision 1.13
diff -u -p -r1.13 eh-common.h
--- gcc/eh-common.h 2000/07/22 23:29:14 1.13
+++ gcc/eh-common.h 2001/03/24 23:32:24
@@ -1,5 +1,5 @@
 /* EH stuff
-   Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
+   Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
 
 This file is part of GNU CC.
 
@@ -40,10 +40,13 @@ Foundation, 59 Temple Place - Suite 330,
    the location of 'dynamic_handler_chain'. If its location is changed, 
    that routine must be modified as well. */
 #ifndef EH_ALLOC_SIZE
-/* 192 bytes means the entire eh_context plus malloc overhead fits in 256
-   bytes (assuming 8 byte pointers). 192 bytes gives an eh_info and object
-   size limit of 96 bytes. This should be sufficient for throwing bad_alloc. */
-#define EH_ALLOC_SIZE 192
+/* 240 bytes are required in the worst case, assuming pointers and
+   longs are 64-bits wide.  When re-throwing an exception whose size
+   is smaller than EH_ALLOC_ALIGN, two cp_eh_info plus two copies of
+   the exception object must be held, in addition to the
+   EH_ALLOC_ALIGN padding between them.  This should be sufficient for
+   throwing bad_alloc.  */
+#define EH_ALLOC_SIZE 240
 #endif
 #ifndef EH_ALLOC_ALIGN
 /* We can't use BIGGEST_ALIGNMENT, because on some systems, that expands to

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me