I have this source file
//src.c
#include "include/headers/my_header.h"
And gcc fails with this error include/headers/my_header.h: No such file or directory
gcc my_src/src.c -Iinclude/headers
However, it works fine if I rewrite the source file like so:
//src.c
#include "my_header.h"
Now, I'm actually compiling a project I've inherited so I'm not trying to rewrite all of the include statements. What gives?
The path after -I catenated to whatever is in the #include statement has to match a path in your file system. Try -I., that leads to ./include/headers/my_header.h, and presumably will let GCC find your header.
Related
I created a very simple hello world program in C and I'm trying to call a function from an included file. The problem is the gcc program is strange in how it recognizes files.
Suppose the main file is named a.c and the file I want to include is b.c
So in my headers, I add:
#include <./b.c>
and when I run gcc 5.3.0, I receive this error:
./a.c:xx:yy: fatal error: ./b.c: No such file or directory
compilation terminated.
(where xx is the line number of the include line and yy is where the > is located on that line.)
I also tried another idea. I executed gcc while including the library path as follows:
gcc -I./ a.c
and I still get the same error.
In all tests, the file b.c exists in the same folder as a.c is and that I execute gcc from.
Now If I change the include line in the source to the following:
#include </path/to/b.c>
(thereby replacing the relative path with an absolute path) and run gcc, the file is then read for processing.
Is there a way I can change my code so I don't have to constantly specify absolute paths if I need to include multiple custom C files that are all in the same folder as the code that references them?
Like... is there such thing as....
#setlibpath /path/to/my/c/files
#include <./item.c>
#include <./item2.c>
....
#include <./itemn.c>
or do I have to do this....
#include </path/to/my/c/files/item1.c>
#include </path/to/my/c/files/item2.c>
....
#include </path/to/my/c/files/itemn.c>
Converting my comments into an answer.
Use double quotes around the name and the header (source file) will be found. Use angle brackets around system headers. And generally, avoid using ./ (and ../ even more so) in header names. For GCC, see also Include Operation and the following sections.
Also see the POSIX specification for the c99 compiler for the -I option:
Change the algorithm for searching for headers whose names are not absolute pathnames to look in the directory named by the directory pathname before looking in the usual places. Thus, headers whose names are enclosed in double-quotes ("") shall be searched for first in the directory of the file with the #include line, then in directories named in -I options, and last in the usual places. For headers whose names are enclosed in angle brackets (<>), the header shall be searched for only in directories named in -I options and then in the usual places. Directories named in -I options shall be searched in the order specified. If the -I option is used to specify a directory that is one of the usual places searched by default, the results are unspecified.
Note that ./b.c is not an absolute pathname — so the name is appended to a set of directories, and the current directory is not used unless the #include line uses double quotes.
I have a C program that has #include <microtime.h> in the header, but when I compile it with GCC or g++, it shows the error -
fatal error: microtime.h: No such file or directory
2 | #include <microtime.h>
How could I compile it. I am not sure if I need to download this microtime separately?
use quotes:-
#include "microtime.h"
Using quotes will look in the same directory first, and then in the specified include paths. Using angle brackets <> will look in the include paths only.
I am looking at FreeRTOS demo project for an AVR port. The Makefile has paths to the directories where the source files of RTOS are located through an "-I" directive. However, in the main.c module of the project #include does not provide any path like this:
#include "FreeRTOS.h"
So I am not able to understand is that is the "-I" directive required only for linker to find the object files? Does it also mean that once the files are compiled to object code, for GCC they are essentially lying in the same folder if it knows where to look?
I have this confusion because I have seen #include statements like these previously:
#include <avr/io.h>
If GCC already knows the location of io.h why include the "avr" part in front of it?
When we say
#include <foo/bar.h>
the compiler usually looks for a file called bar.h in a directory called foo in one of the places it is configured to look for headers. For example, the standard header search path usually contains `/usr/include', so a file 'bar.h' will be found, if it exists, in '/usr/include/foo'.
If you use the -I switch like this:
-I /usr/include/foo
you could alternatively write
#include <bar.h>
because you've subsumed the directory foo into the compiler's header search path.
However, if foo is some kind of library or module, it's probably more expressive to use a variant of #include that includes the subdirectory foo, rather than manipulating the header search path so that you don't have to.
For the record, the -I switch has no direct effect on linking behaviour.
Incidentally, the variant
#include "foo/bar.h"
conventionally indicated a file in a directory foo in the same directory as the source file. However, modern compilers seem to apply search header paths to these directives as well. I'm not sure whether this is standards-based behaviour, or just compiler writers trying to guess our intentions.
Imagine that I have a C-project in the following folder:
C:\microcontroller\stm32\myProject
I have two important folders inside myProject:
- source => here are all my .c and .h files
- build => gcc will write all the object files in here
Note: as you can see, the backward slashes indicate that this is happening on a Windows pc.
The figure below gives an overview:
I will not display my complete makefile here, because that would lead us too far. The rules inside the makefile for all .c => .o files are similar. Let us just focus on the compilation of one specific file: fileA2.c:
--------------------- COMPILATION OF FILE fileA2.c -------------------
Building ./build/folderA/fileA2.o
arm-none-eabi-gcc C:\\microcontroller\\stm32\\myProject\\source\\folderA\\fileA2.c
-o C:\\microcontroller\\stm32\\myProject\\build\\folderA\\fileA2.o
-c
-MMD
-mcpu=cortex-m7
-...
-IC:/microcontroller/stm32/myProject/source/folderA
-IC:/microcontroller/stm32/myProject/source/folderB
Notice that the gcc call ends with two include flags: one for folderA and one for folderB. This enables gcc to use any of the header files from these folders (fileA1.h, fileA2.h or fileB1.h) if fileA2.c has an import statement.
Let us now consider the source code in fileA2.c. We assume that this file needs to include fileA2.h and also fileB1.h.
/*******************************/
/* SOURCE CODE fileA2.c */
/*******************************/
// Some include statements
#include "fileA2.h"
#include "fileB1.h"
// Code
...
These include statements work perfectly. The gcc compiler retrieves the files fileA2.h and fileB1.h in the given folders. But I noticed that the following does not work:
/*******************************/
/* SOURCE CODE fileA2.c */
/*******************************/
// Some include statements
#include "fileA2.h"
#include "folderB/fileB1.h"
// Code
...
The last include statement is a 'partial path' to the file. I get the error when compiling:
fatal error: folderB/fileB1.h: No such file or directory
How can I get gcc to handle this?
PS: It is not my own habit to use 'partial paths'. But they appear a lot in the libraries from the silicon vendor of my chip, so I have to live with it.
You specify two paths to look for includes other than the current directory for the source file:
-IC:/microcontroller/stm32/myProject/source/folderA
-IC:/microcontroller/stm32/myProject/source/folderB
You get the error because neither
C:/microcontroller/stm32/myProject/source/folderA/folderB/fileB1.h nor
C:/microcontroller/stm32/myProject/source/folderB/folderB/fileB1.h exists.
To address the error, you can add the following path:
-IC:/microcontroller/stm32/myProject/source
When using double-quotes to include a header file the compiler first looks in the same directory as the current file. If the header file is not found then it continues with the standard include search paths.
So when the compiler compiles the file source/folderA/fileA2.c the first directory the compiler will look for include files is the source/folderA directory. In the first example the fileB1.h will not be found there, but since you added source/folderB to the standard search path it will be found there as source/folderB/fileB2.h.
In the second example there is no folderB/fileB1.h file on source/folderA so the compiler will search the standard search path. When it comes to source/folderB it will again try folderB/fileB2.h (i.e. source/folderB/folderB/fileB2.h) and it will still not be found, nor will it be found anywhere else.
You need to add -IC:/microcontroller/stm32/myProject/source to be able to find folderB/fileB1.h.
Apart of the two correct responses you have received before this, you have the third chance to specify the path to the file in the #include directive from the curren directory, as with
`#include "../folderB/fileB1.h"
I want to compile a C program in gcc which has my 2 header files.
I am using the command:
gcc UDP_Receive.c -o UDP_Receive -lm
to compile it but I get an error stating "UDP_Data.h: No such file or directory"
How can I tell the compiler to include these header files?
Header Files:
#include "UDP_Data.h"
#include "Crypt.h"
Thanks,
Ritesh
Use -Idirectory to add include paths, or make your #include statement use relative paths.
EDIT:
Also be aware that #include filenames are case sensitive on many platforms.
EDIT2:
Use #include "UDP_Data.h" not #include <UDP_Data.h>
You have told the compiler to include that file, with a line like this:
#include "UDP_Data.h"
the problem is that the compiler can't find that file, and don't forget that some platforms are case sensitive when it comes to filenames so "UDP_data.h" is not the same file as "UDP_Data.h". The compiler will serach in a few places by default, but you will need to add extra directories to its search by using command line options. The exact option will depend on the compiler, for gcc it's:
-I<directory>