Hi! I have a modification of GCC that includes a call to mprotect from a signal handler. Applications compiled with the altered GCC work fine (at least as far as I can tell) if I edit my GCC Makefile before compiling GCC so as to eliminate the default "-O2" flag. If I restore the optimization, however, and recompile GCC and then the application under that GCC, the application fails: mprotect reports ENOMEM. Any ideas, either on this problem or on how I should go about investigating it? A few background details: The alteration is the beginning of a new implementation of OpenMP. Among other differences, whereas the original implementation is built atop internal calls to the pthread machinery, this implementation is based on fork: each "thread" is a separate process under the OS (Linux). When each thread starts, it calls mprotect to set its heap and static data (BSS) segments to read-only, so that it can trap any first write to a page. On the first write to a page, the signal handler records which page the thread has written to in a separate (read-write, of course) data structure, and resets the current page to read-write. The version of GCC I am altering is 4.5.2 . I am running it and the target application under Ubuntu Linux 10.04.2 Server (x86_64) with kernel 2.6.32-server on a 64-bit AMD machine with 12 cores. Thanks! Amittai Aviram PhD Student in Computer Science Yale University 646 483 2639 amittai.aviram@xxxxxxxx http://www.amittai.com
