mkdir cs45 cd cs45 pwd mkdir weelylabs cd weeklylabs mkdir w01 cd w01 pwd cp ~newhall/public/cs45/week01/* . ls
Try looking at the man page for fork to see how it is telling you information about the fork function: how to call it; what header file(s) to be included to call it; and what the function does and what its return value(s) are.
% man fork # or, I could specify the man section...I don't need to for fork: % man 2 fork # the man page for the system call fork in section 2 of the manual
We will try running this and use the kill command to send the process signals:
kill -INT 1234 # sends a SIGINT signal to process 1234Let's try running the program and see what it is doing.
The man page for signal lists the signals on this system and
describes the signal system call in more detail.
Here is a directory of files you can copy over that can be used to test out some gdb features:
cd ~/cs45/weeklylabs cp -r ~newhall/public/gdb_examples . cd gdb_examplesFirst, run make to build the executables (note they are all compiled with -g).
Let's look through a couple of the example programs in gdb, following along in my GDB Guide.
One example program that you may want to try out is the fork_example.c. It can be used to test out the gdb support for specify which process gdb should follow on a fork (either the parent XOR the child):
(gdb) set follow-fork-mode child (gdb) set follow-fork-mode parent # gdb's default behavior
Up the page on this guide are lists of common gdb commands and some examples
of how to use them.
Valgrind is a tool for finding heap memory access errors and memory leaks in C and C++ programs. Memory access errors are often very difficult bugs to find, and valgrind helps you easily find errors like reads or writes beyond the bounds of a malloc'ed array, accessing free'ed memory, reading uninitialized memory, and memory leaks (not freeing malloc'ed space before all variables referring to it go out of scope).
Here are some files you can copy over that can be used to test out valgrind:
cd ~/cs45/weeklylabs cp -r ~newhall/public/valgrind_examples . cd valgrind_examplesTo use valgrind, just compile with -g, and run valgrind on your program (the Makefile has this already):
make valgrind ./badprogThe output at first seems a bit cryptic, but once you see the basics of how to interpret it, it is extremely helpful for finding and fixing memory access errors. Let's look at my Valgrind Guide to see how to interpret some of this valgrind output. This guide contains links to other valgrind resources, and the README file in the code you copied over lists some command line options for running valgrind.
Some more information on debugging tools for C: C programming tools: gdb and valgrind