How do i know which .h file the compiler is using?
ProgrammingThis forum is for all programming questions.
The question does not have to be directly related to Linux and any language is fair game.
Notices
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Get a virtual cloud desktop with the Linux distro that you want in less than five minutes with Shells! With over 10 pre-installed distros to choose from, the worry-free installation life is here! Whether you are a digital nomad or just looking for flexibility, Shells can put your Linux machine on the device that you want to use.
Exclusive for LQ members, get up to 45% off per month. Click here for more info.
Distribution: WinXP SP2 and SP3, W2K Server, Ubuntu
Posts: 313
Rep:
How do i know which .h file the compiler is using?
I am trying to learn Linux by looking at source code and writing some of my own. Thank goodness its open source. Anyway, Iwant to knwo where the .h and .c files are located. For example, to find unistd.h, I did a
Unless you have a horribly mutated installation, the preprocessor grabs the files from /usr/include/ (e.g. #include <stdio.h> is the same as #include "/usr/include/stdio.h")
(You have to hunt for this output among the rest of the stuff it prints out). The file it loads will be the first one it finds looking through those directories in order.
If and only if there is a file called unistd.h in that directory. Otherwise it will look in each directory until it finds one. You should be suspicious of any unistd.h file in either of those first two directories.
Because a file as basic as unistd would usually be in /usr/include, and if there was a copy in one of those other directories, it would be used first, and could potentially contain exploit code. It would be a strange form of attack, and quite unlikely (I think), but possible. Many projects you might compile from source would make use of unistd.
LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.