C programming notes - Revision history

Ted: Add subsection q To use GCC to see macro expansion q

2026-03-04T16:04:12Z

Add subsection q To use GCC to see macro expansion q

Ted: Add top-of-page links in subsection titles, add link to new local page to create

2026-02-26T18:17:42Z

Add top-of-page links in subsection titles, add link to new local page to create

Ted: Add subsection q CONTAINER_OF macro q

2026-02-26T18:15:39Z

Add subsection q CONTAINER_OF macro q

Ted: X macro idiom : add link to Phillip Trudeau X Macro blog post

2026-01-23T21:34:26Z

X macro idiom : add link to Phillip Trudeau X Macro blog post

Ted: Remove stale note

2026-01-22T15:19:46Z

Remove stale note

Ted: C Macros : C preprocessor does not expand arguments to `#` directive

2026-01-22T15:19:13Z

C Macros : C preprocessor does not expand arguments to `#` directive

Ted: C Macros : add link to home dot cs dot colorado dot edu and create sub-sections

2026-01-22T15:13:02Z

C Macros : add link to home dot cs dot colorado dot edu and create sub-sections

Ted: Macro examples from Zephyr RTOS release 3.7.1

2026-01-21T22:23:23Z

Macro examples from Zephyr RTOS release 3.7.1

Ted: Add note on FOREACH macros

2026-01-21T18:23:17Z

Add note on FOREACH macros

Ted: /* ^ C Macros */

2026-01-21T06:04:12Z

^ C Macros

← Older revision		Revision as of 16:04, 4 March 2026
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	See also 2026 Q1 local page on [[developers\|developers]].		See also 2026 Q1 local page on [[developers\|developers]].
		+
		+	=== [[#top\|^]] To use GCC to see macro expansion ===
		+
		+	Here is an example shell script which invokes gcc on a single C source file, and causes only the preprocessor to execute. This results in a display of all preprocessor macros:
		+
		+	<pre>
		+	#!/bin/bash
		+
		+	# References:
		+	# * https://gcc.gnu.org/onlinedocs/gcc-3.2.2/cpp/Search-Path.html
		+
		+	# $workspace/zephyr/subsys/testsuite/include/zephyr/fff.h
		+
		+	gcc -E \
		+	-I../../../../../zephyr/subsys/testsuite/include \
		+	-I../../../../../zephyr/include \
		+	./unit-test-mocked-functions.h
		+
		+	exit $?
		+	</pre>

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@@ Line 171: / Line 171: @@
 # https://en.wikipedia.org/wiki/X_macro<br />
-=== do while(0) ===
+=== [[#top|^]] do while(0) ===
 Articles on the use of C language 'do while(0)' construct in macros.  The do while(0) construct is the only C syntax which expands correctly from C macros regardless of the use of curly braces and semicolons around the given macro.
@@ Line 177: / Line 177: @@
 *  https://hownot2code.wordpress.com/2016/12/05/do-while-0-in-macros/
-=== stringification macro pair ===
+=== [[#top|^]] stringification macro pair ===
 A useful macro pair, and this must be a macro pair, is the following set of defines.  These defines will accept a string and put double quotes around it:
@@ Line 191: / Line 191: @@
 The core rule at play is that C preprocessor does not expand macros preceded by the `#` preprocessor directive, the directive to quote a token.  By creating a wrapping macro which does not call the `#` directive, the argument to the wrapper is expanded and then passed to the quoting directive.
-=== fallthrough macro ===
+=== [[#top|^]] fallthrough macro ===
 The `__fallthrough()` macro appears to be a C++ macro.  It may be found among Zephyr RTOS 3.4.0 source tree contents.  An article on the concept of "fall through" in C switch statements:
@@ Line 197: / Line 197: @@
 *  https://www.quora.com/What-is-the-fall-through-behavior-in-C-programming-languages-switch-case-statements
-=== X macro idiom ===
+=== [[#top|^]] X macro idiom ===
 X macros in C, a pattern involving nested macros makes use of nesting an initially declared and not defined macro within another macro.  Danilafe and Phillip Trudeau offer the following blog posts on this topic:
@@ Line 208: / Line 208: @@
 *  https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
-=== FOREACH macro implementations (may not be fully possible) ===
+=== [[#top|^]] FOREACH macro implementations (may not be fully possible) ===
 *  https://dev.to/sgf4/foreach-macro-in-c-48ic
@@ Line 221: / Line 221: @@
 ```
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+=== [[#top|^]] CONTAINER_OF macro ===
 Helpful blogpost by Radek Pazdera, full-stack software engineer based in London . . .
 * https://radek.io/posts/magical-container_of-macro/
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@@ Line 220: / Line 220: @@
 ./include/zephyr/devicetree.h:4544:#define DT_INST_FOREACH_STATUS_OKAY_VARGS(fn, ...) \
 ```
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@@ Line 199: / Line 199: @@
 === X macro idiom ===
-X macros in C, a pattern involving nested macros:
+X macros in C, a pattern involving nested macros makes use of nesting an initially declared and not defined macro within another macro.  Danilafe and Phillip Trudeau offer the following blog posts on this topic:
 *  https://danilafe.com/blog/chapel_x_macros/
 Macro tips and idioms:

← Older revision		Revision as of 15:19, 22 January 2026
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	* https://www.quora.com/What-is-the-fall-through-behavior-in-C-programming-languages-switch-case-statements		* https://www.quora.com/What-is-the-fall-through-behavior-in-C-programming-languages-switch-case-statements
−
−	~~Some larger introductions and discussions of C preprocessor and C macros are found at these four references:~~

	=== X macro idiom ===		=== X macro idiom ===

@@ Line 188: / Line 188: @@
 *  https://www.guyrutenberg.com/2008/12/20/expanding-macros-into-string-constants-in-c/
 </ul>
 === fallthrough macro ===

@@ Line 163: / Line 163: @@
 == [[#top|^]] C Macros ==
-This section likely to grow as C macros have a development history somewhat separate from the development of C language itself, and extensive use being both powerful and prone to pitfalls.
+This section likely to grow as C macros have a development history somewhat separate from the development of C language itself, and extensive use being both powerful and prone to pitfalls.  Some general and comprehensive discussions of C macros can be found at:
 Articles on the use of C language 'do while(0)' construct in macros.  The do while(0) construct is the only C syntax which expands correctly from C macros regardless of the use of curly braces and semicolons around the given macro.
 *  https://hownot2code.wordpress.com/2016/12/05/do-while-0-in-macros/
 A useful macro pair, and this must be a macro pair, is the following set of defines.  These defines will accept a string and put double quotes around it:
-    #define MAKE_STRING_QUOTED(string) #string
+    #define TO_QUOTE_STRING(string) #string
-    #define WRAPPER_NEEDED_TO_QUOTE_STRING(token) MAKE_STRING_QUOTED(string)
+    #define WRAPPER_TO_QUOTE_STRING(token) TO_QUOTE_STRING(string)
-One Guy Rutenberg explains this C pre-processor pattern:
+Guy Rutenberg explains this C pre-processor pattern:
 <ul>
 *  https://www.guyrutenberg.com/2008/12/20/expanding-macros-into-string-constants-in-c/
 </ul>
-This C macro pattern is explained a number of other places as well.
+=== fallthrough macro ===
 The `__fallthrough()` macro appears to be a C++ macro.  It may be found among Zephyr RTOS 3.4.0 source tree contents.  An article on the concept of "fall through" in C switch statements:
@@ Line 188: / Line 197: @@
 Some larger introductions and discussions of C preprocessor and C macros are found at these four references:
-  # https://stackoverflow.com/questions/4674480/do-whilefalse-pattern<br />
+=== X macro idiom ===
 X macros in C, a pattern involving nested macros:
@@ Line 201: / Line 207: @@
 *  https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
-FOREACH macro implementation:
+=== FOREACH macro implementations (may not be fully possible) ===
 *  https://dev.to/sgf4/foreach-macro-in-c-48ic

← Older revision		Revision as of 22:23, 21 January 2026
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	* https://dev.to/sgf4/repeat-macro-in-c-2hh0		* https://dev.to/sgf4/repeat-macro-in-c-2hh0
		+
		+	Macro examples from Zephyr RTOS release 3.7.1:
		+
		+	```
		+	./include/zephyr/devicetree.h:4527:#define DT_INST_FOREACH_STATUS_OKAY(fn) \
		+	./include/zephyr/devicetree.h:4544:#define DT_INST_FOREACH_STATUS_OKAY_VARGS(fn, ...) \
		+	```

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← Older revision		Revision as of 18:23, 21 January 2026
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	* https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms		* https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
		+
		+	FOREACH macro implementation:
		+
		+	* https://dev.to/sgf4/foreach-macro-in-c-48ic
		+
		+	* https://dev.to/sgf4/repeat-macro-in-c-2hh0

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← Older revision		Revision as of 06:04, 21 January 2026
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	* https://danilafe.com/blog/chapel_x_macros/		* https://danilafe.com/blog/chapel_x_macros/
		+
		+	Macro tips and idioms:
		+
		+	* https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms

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