How GCC locates included files - Versionsgeschichte

Wolfgang am 22. Mai 2020 um 20:11 Uhr

2020-05-22T20:11:20Z

← Nächstältere Version		Version vom 22. Mai 2020, 20:11 Uhr
Zeile 53:		Zeile 53:
	End of search list.		End of search list.
	</pre>		</pre>

			== Compiler Options to control where GCC looks for include files ==

			There are a number of options when invoking the GCC compiler to control which file system locations are include-files looked up in:

			https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html#Directory-Options

Wolfgang am 21. Mai 2020 um 16:24 Uhr

2020-05-21T16:24:22Z

← Nächstältere Version		Version vom 21. Mai 2020, 16:24 Uhr
Zeile 15:		Zeile 15:
	* Quote-Syntax looks like: <code>#include "library_header.h"</code>		* Quote-Syntax looks like: <code>#include "library_header.h"</code>
	* Angle-Bracket-Syntax looks like <code>#include <library_header.h></code>		* Angle-Bracket-Syntax looks like <code>#include <library_header.h></code>

			The difference between these 2 variants is the location(s) the compiler looks for the files to be included.

			== Built-in default locations in the compiler ==

			The default locations where the compiler looks for include-files are determined when building the compiler itself.

			For the AVR-GCC used in [[Arduino]] 1.8.12, the documentation says:

			...

			The Command

			<code>echo \| gcc -Wp,-v -x c++ - -fsyntax-only</code>

			shows the directories the GCC compiler looks up for includes.

			Example:

			<pre>
			ignoring nonexistent directory "c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/../../../../avr/include/c++/7.3.0"
			ignoring nonexistent directory "c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/../../../../avr/include/c++/7.3.0/avr"
			ignoring nonexistent directory "c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/../../../../avr/include/c++/7.3.0/backward"
			ignoring nonexistent directory "c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/../../../../avr/sys-include"
			ignoring nonexistent directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/../../../../avr/include/c++/7.3.0"
			ignoring nonexistent directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/../../../../avr/include/c++/7.3.0/avr"
			ignoring nonexistent directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/../../../../avr/include/c++/7.3.0/backward"
			ignoring duplicate directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/include"
			ignoring duplicate directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/include-fixed"
			ignoring nonexistent directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/../../../../avr/sys-include"
			ignoring duplicate directory "c:/program files (x86)/arduino/hardware/tools/avr/lib/gcc/../../lib/gcc/avr/7.3.0/../../../../avr/include"
			#include "..." search starts here:
			#include <...> search starts here:
			c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/include
			c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/include-fixed
			c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/7.3.0/../../../../avr/include
			End of search list.
			</pre>

Wolfgang am 21. Mai 2020 um 14:06 Uhr

2020-05-21T14:06:58Z

← Nächstältere Version		Version vom 21. Mai 2020, 14:06 Uhr
Zeile 5:		Zeile 5:
	'''SO,''' one of the most asked questions in the interwebs about the C-compiler is: "where the hell does the C-compiler look for included files" (with more or less expletives included".		'''SO,''' one of the most asked questions in the interwebs about the C-compiler is: "where the hell does the C-compiler look for included files" (with more or less expletives included".

	''THE ANSWER''' is (as usual): ''it depends ...''		'''THE ANSWER''' is (as usual): ''it depends ...''

	As I was not really satisfied with what I could read, mainly because the concrete information was spread out all over the place, I'm trying to compile (sic!) the definitive information on the topic, but for one selected scenario:		As I was not really satisfied with what I could read, mainly because the concrete information was spread out all over the place, I'm trying to compile (sic!) the definitive information on the topic, but for one selected scenario:

Wolfgang am 21. Mai 2020 um 14:06 Uhr

2020-05-21T14:06:37Z

← Nächstältere Version		Version vom 21. Mai 2020, 14:06 Uhr
Zeile 1:		Zeile 1:
	It is a constantly raised issue: you write a C-program using a library. You <code>#include "library_header.h"</code> or <code>#include <library_header.h></code>~~. BUT: Not all is well: either your .h-file could not be found or another equally-named .h-file is included, ..~~.		It is a constantly raised issue: you write a C-program using a library. You <code>#include "library_header.h"</code> or <code>#include <library_header.h></code>.

	~~So, one of the most asked questions in the interwebs about the C-compiler~~ is: ~~"where the hell does the C~~-~~compiler look for included files" (with more~~ or ~~less expletives~~ included".		'''BUT:''' Not all is well: either your .h-file could not be found or another equally-named .h-file is included, ...

	~~The answer~~ is (as usual): ''it depends ...''		'''SO,''' one of the most asked questions in the interwebs about the C-compiler is: "where the hell does the C-compiler look for included files" (with more or less expletives included".

			''THE ANSWER''' is (as usual): ''it depends ...''

	As I was not really satisfied with what I could read, mainly because the concrete information was spread out all over the place, I'm trying to compile (sic!) the definitive information on the topic, but for one selected scenario:		As I was not really satisfied with what I could read, mainly because the concrete information was spread out all over the place, I'm trying to compile (sic!) the definitive information on the topic, but for one selected scenario:

Wolfgang: Die Seite wurde neu angelegt: „It is a constantly raised issue: you write a C-program using a library. You `#include "library_header.h"` or `#include <library_header.h>…“`


2020-05-21T14:04:19Z
Die Seite wurde neu angelegt: „It is a constantly raised issue: you write a C-program using a library. You <code>#include "library_header.h"</code> or <code>#include <library_header.h>…“
Neue Seite
It is a constantly raised issue: you write a C-program using a library. You <code>#include "library_header.h"</code> or <code>#include &lt;library_header.h&gt;</code>. BUT: Not all is well: either your .h-file could not be found or another equally-named .h-file is included, ...



So, one of the most asked questions in the interwebs about the C-compiler is: "where the hell does the C-compiler look for included files" (with more or less expletives included".



The answer is (as usual): ''it depends ...''



As I was not really satisfied with what I could read, mainly because the concrete information was spread out all over the place, I'm trying to compile (sic!) the definitive information on the topic, but for one selected scenario:



* the AVR-GCC compiler used in the [[Arduino]] 1.8.12 development environment, running on Microsoft Windows 10. This should eliminate the "it depends.." factor by nailing down all variations to a specific constellation.



== Quote-Syntax versus Angle-Bracket-Syntax for #include ==



* Quote-Syntax looks like: <code>#include "library_header.h"</code>

* Angle-Bracket-Syntax looks like <code>#include &lt;library_header.h&gt;</code>

How GCC locates included files - Versionsgeschichte

Wolfgang am 22. Mai 2020 um 20:11 Uhr

Wolfgang am 21. Mai 2020 um 16:24 Uhr

Wolfgang am 21. Mai 2020 um 14:06 Uhr

Wolfgang am 21. Mai 2020 um 14:06 Uhr

Wolfgang: Die Seite wurde neu angelegt: „It is a constantly raised issue: you write a C-program using a library. You #include "library_header.h" or #include <library_header.h>…“

Wolfgang: Die Seite wurde neu angelegt: „It is a constantly raised issue: you write a C-program using a library. You `#include "library_header.h"` or `#include <library_header.h>…“`