Hello all, I'm attempting to do some work with the sysctl interface from a module. I am able to correctly build my module using make modules but I get the "undefined reference to errno" when I attempt the make modules_install step. Some trawling on the net has revealed that this started happening with various source trees using older conventions e.g. from http://www.compusys.co.uk/Compusys/HPC/Cluster+Admin+Tips/Compilation+errors+with+GCC+Version+3.2+and+Open+PBS+version+2.3.16.htm ------------------------------------------------------- "Since version 2.9 of the GCC compiler the compiler has become a lot stricter over declaring external references. Undefined reference to ?errno? In most cases this is not a problem, but only when the programming of a library has become slightly lax. Once common error is to use the phrase: extern int errno; in c code rather than the correct method of: #include <errno.h> This can be seen in a few of the libraries supplied with Open PBS. To fix this problem cd to the directory which includes the source code and type the following command: grep -rs ?extern int errno? * If any files return as having the line, then replace the line with the correct version as shown above, using your favourite text editor." ------------------------------------------------------- When I run this against my development tree, the only place errno is defined is in include/linux/unistd.h I notice on the lxr site that this is currently valid code. For some background, my module is a networking component and I need to fetch some /proc info. Since I am in the kernel I can't use the userspace sysctl lib and have to: #include <linux/sysctl.h> #include <linux/unistd.h> and use the syscall1 macro. This part of the code seems fine. In order to test it, I tried a small userspace program which generated the same "unreferenced errno" error until I did the following : #include <linux/errno.h> Now the userspace example works but it doesn't fix the module. WTF is going on here? I don't know enough about this to fix it but I'd be grateful for any pointers even if its to a site or book worth reading about this because I know my ignorance of compiling and linking isn't helping me here. I have taken a look at Johnson & Troans "Linux Application Development" and Rubini's "Understanding the Linux Kernel" but there is very little discussion of the linking phase of a kernel build. There are so many returns for this on google that it must have tripped up a few people - just none of the solutions match my problem. Any help gratefully received, cam __________________________________ Do you Yahoo!? Yahoo! Mail SpamGuard - Read only the mail you want. http://antispam.yahoo.com/tools -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
