How headers are included though the path is not showing the header folder

mnowhere · 07-21-2012, 02:55 PM

I have written a simple helloworld.c to print "hello world" message.
This uses stdio.h file which is located /usr/include/. my path does not include the path /usr/include at all then how does the gcc picks stdio.h when i compile d source.

pixellany · 07-21-2012, 02:59 PM

Your path tells the system where to look when you run a command----including running gcc. When gcc is running, it has its own path definition telling it where to find things.

mnowhere · 07-21-2012, 11:25 PM

Quote:

Originally Posted by pixellany

When gcc is running, it has its own path definition telling it where to find things.

How can I see the gcc's path definition? If I need to have one header file to be defined in the gcc's path how can I do it?

pixellany · 07-22-2012, 05:07 AM

Look for some kind of configuration file---I assume this would be in /etc, but it could also be in your ~ directory.

Brute force method:
Run this as root:

Code:

find / -name "*gcc*conf"
or maybe
find / -name "*gcc*cfg"

But doesn't gcc also have some command options for setting things up? e.g. try "man gcc"

Nylex · 07-22-2012, 06:31 AM

http://gcc.gnu.org/ml/gcc-help/2007-09/msg00204.html

Also, note that sometimes you do have to tell gcc (well, technically the preprocessor) where to find headers and libraries. You do this with the -I and -L options, respectively.

Wim Sturkenboom · 07-22-2012, 07:29 AM

Quote:

Originally Posted by mnowhere

... If I need to have one header file to be defined in the gcc's path how can I do it?

If you're talking about your own header files, you can put them in the same directory as your code; they are, after all, part of your project.

Code:

+
|
+-- yourproject
       |
       +-- main.c
       +-- somefile.c
       +-- someinclude.h

And in main.c and/or somefile.c, you can simply include someinclude.h and the compiler will find them.

mnowhere · 07-31-2012, 02:39 PM

Thnq Nylex and everyone,

The following link,
http://gcc.gnu.org/ml/gcc-help/2007-09/msg00204.html
explains about the include path very well, the include path for the header files is taken care by preprocessor(cpp) and not the compiler(gcc)
so executing "cpp -v" on command prompt will give u the list of paths where the c preprocessor looks for header files by default.

But how to edit this path is still being mystery for me, I am expecting some help from u guys..

Nylex · 07-31-2012, 02:41 PM

Why can't you use the -I option to specify additional directories?

mnowhere · 08-01-2012, 02:39 AM

Quote:

Originally Posted by Nylex

Why can't you use the -I option to specify additional directories?

There is no problem in doing dat.. Its just for the sake of my knowledge.. jus wanted to kno if I change or add the header file path..

Nylex · 08-05-2012, 07:02 AM

I think (but am not at all certain) that the directories are specified when the compiler is built, so you have to use the -I option.

Also, per the LQ rules, please avoid "SMS" speak and write out your words in full.

mnowhere · 08-07-2012, 03:34 AM

I am extremely sorry for those SMS kind of messages

it has became a habit for me