http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59178
Bug ID: 59178
Summary: Stack corruption on register save/restore when using
frame pointer on pdp-11
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: blocker
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: martin.alcock at praebius dot ca
Created attachment 31239
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31239&action=edit
simple C functions and their assembly prologues/epilogues
When targeting the pdp-11 and more than one register has to be saved in the
function pologue, different modes are used for the save and restore in the
epilogue that causes stack corruption.
In the prologue, the registers are pushed onto the stack using a "-(sp)",
syntax, however when restored in the epilogue the "xx(fp)" syntax is used
instead, thus not correcting the stack pointer on the restore. R5 is used as
the frame pointer. This causes the code to go wild, as it returns to an address
that previously contained arbitrary register contents.
Attached is a file showing the C source from some small routines and the
assembly code for the prologue and epilogue.
