Thanks Paul, I know we can’t use standard C functions. The only reason I wanted to check here is whether the parent make is also getting ctrl+c ( which it isn’t). Do you suggest calling die from within fatal signal handler ?
My requirement is to perform a task( write to a file) only ONCE when I give ctrl C . Which place in the code is best to do so? Thanks Nikhil On Sun, 22 May 2022 at 4:57 AM, Paul Smith <psm...@gnu.org> wrote: > On Sat, 2022-05-21 at 08:37 +0530, nikhil jain wrote: > > Also, fatal error handler in commands.C gets called multiple times. I > > believe it is getting called for each parallel make process the > > parent has invoked. > > Certainly. When you press ^C make will propagate that signal to all > its children so that any compile commands, etc. are properly killed. > This is an absolute requirement: you don't want your compiler to keep > running after you've killed make! > > This means every sub-make (which is just another recipe to run, to > make) will also receive a SIGINT. > > > 1) why the die() function is not getting called after a ctrl+c ? > > Sorry, I misread the code. I thought that the fatal function would > invoke die() (eventually) but I see now that that only happens if it > fails to kill itself the "normal" way. > > So make will exit through die() for "normal" exits and through the > fatal function for exits caused by signals (like ^C). Two different > places. > > > 2) why I am not able to printf anything in fatal error handler in > > commands.c ? I do printf but it doesn’t print on the screen. The > > stdout is gone? > > This method is invoked inside a signal handler. You cannot, generally, > use standard C runtime functions such as printf() inside a signal > handler. Because a signal is asynchronous, it could interrupt ANY > operation including right in the middle of a malloc() call or free() or > some other printf(), etc. and you can't assume anything about the state > of the program. > > There are a limited number of system calls you can invoke from within a > signal handler. Knowing how to write good signal handler code is an > entire area of study and not related to GNU make really. There are > docs and tutorials on it out there. > >
