From: Wang Nan <wangnan0@xxxxxxxxxx> Subject: [PATCH 3/4] makedumpfile: add -D_GNU_SOURCE to CFLAGS Date: Sat, 26 Apr 2014 12:07:08 +0800 > This patch is preparation for introduce pread/pwrite. > Do you explain more about _GNU_SOURCE? Did you need to define this on your environment to build makedumpfile with pread/pwrite? I tried to build a very simple test program using pread like int main(void) { printf("%p\n", pread); } on RHEL5.4, RHEL6.5 and fc20, and all were done successfully without _GNU_SOURCE. They are all on x86_64. I checked man pread and man pwrite on each environments for _GNU_SOURCE but I didn't find it. What I found was _XOPEN_SOURCE description only. For example this is man pread on RHEL6.5. $ LANG=C man pread PREAD(2) Linux Programmer's Manual PREAD(2) NAME pread, pwrite - read from or write to a file descriptor at a given offset SYNOPSIS #define _XOPEN_SOURCE 500 #include <unistd.h> ssize_t pread(int fd, void *buf, size_t count, off_t offset); ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset); Note that just as I said the above, building was successfully done on this environment. -- Thanks. HATAYAMA, Daisuke