How to solve Variadic Arguments issue (using C) - Revision history

PoC: Restructured a bit.

2020-02-23T20:46:09Z

Restructured a bit.

← Older revision		Revision as of 22:46, 23 February 2020
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			{{FIXME\|Rephrase, reformat, set links and wade out unneccessary stuff.}}
	First of all, what are Variadic Arguments (VA)?		First of all, what are Variadic Arguments (VA)?
	It's a way to NOT define the number of arguments a function (or method) takes. You only define the args you '''definitely''' going to be given on '''every''' call. All additional arguments are then optional, but can be used if given.		It's a way to NOT define the number of arguments a function (or method) takes. You only define the args you '''definitely''' going to be given on '''every''' call. All additional arguments are then optional, but can be used if given.
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	Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.		Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.

			== Weblinks ==
			* [https://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html GNU.org explaining VA]]

	~~----~~		== Footnotes ==
	* Links		<references />
	** https:~~//gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html GNU.org explaining VA~~
			[[Category: Programming]]

Heiko: /* The code used */

2019-11-28T10:38:55Z

The code used

← Older revision		Revision as of 12:38, 28 November 2019
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	This is how it's used in the code:		This is how it's used in the code:
	Say(0, "Error: Socket creation failed with %s\n", "just a random argument"); // ~~With additional~~ arguments		// TEST W/ ADDITIONAL variadic arguments
	Say(0, "Error: Socket creation failed...\n"); ~~// just a plain message~~		Say(0, "Error: Socket creation failed with %s\n", "just a random argument");

			// EMPTY variadic arguments
			Say(0, "Error: Socket creation failed...\n");

	This is how the define adds the filename and linenumber:		This is how the define adds the filename and linenumber:

Heiko: /* The Solution */

2019-11-28T10:37:40Z

The Solution

← Older revision		Revision as of 12:37, 28 November 2019
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	#define Say(logLevel, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, __VA_ARGS__);		#define Say(logLevel, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, __VA_ARGS__);
	Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.		Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.

Heiko: /* The Solution */

2019-11-28T10:36:36Z

The Solution

← Older revision		Revision as of 12:36, 28 November 2019
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	So what next? I couldn't explain why and how the truncation happened (even after many attempts of understanding/solving this issue) and started to follow the only ~~valid~~ lead: The CZM0041 error, even though was only thrown by one of the two lines.		So what next? I couldn't explain why and how the truncation happened (even after many attempts of understanding/solving this issue) and started to follow the only other lead: The CZM0041 error, even though was only thrown by one of the two lines.

	[https://en.wikipedia.org/wiki/Variadic_macro Wikipedia] states: ''Both the [C99] and [C++11] standards '''require at least one argument''', but since [C++20] this limitation has been lifted through the __VA_OPT__ functional macro. The __VA_OPT__ macro is replaced by its argument when arguments are present, and omitted otherwise. <font color="green">Common compilers also permit passing zero arguments before this addition, however.</font>''		[https://en.wikipedia.org/wiki/Variadic_macro Wikipedia] states: ''Both the [C99] and [C++11] standards '''require at least one argument''', but since [C++20] this limitation has been lifted through the __VA_OPT__ functional macro. The __VA_OPT__ macro is replaced by its argument when arguments are present, and omitted otherwise. <font color="green">Common compilers also permit passing zero arguments before this addition, however.</font>''

Heiko: /* The Solution */

2019-11-28T10:35:38Z

The Solution

← Older revision		Revision as of 12:35, 28 November 2019
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	36 ! Say(0, "Error: Socket creation failed with %s\n", "just a random argument");		36 ! Say(0, "Error: Socket creation failed with %s\n", "just a random argument");
	36 + logWithMethodName("connectAMI", 36, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>		36 + logWithMethodName("connectAMI", 36, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>
	SEVERE==========> a - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>		SEVERE==========> a - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously, this truncated line misses some characters...</font>
	SEVERE==========> b - CZM0045 Undeclared identifier paramete. <font color="red"><--- Obviously this truncated identifier won't work...</font>		SEVERE==========> b - CZM0045 Undeclared identifier paramete. <font color="red"><--- Obviously, this truncated identifier won't work...</font>
	37 !		37 !
	38 ! // EMPTY variadic arguments		38 ! // EMPTY variadic arguments
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	39 + logWithMethodName("connectAMI", 39, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>		39 + logWithMethodName("connectAMI", 39, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>
	ERROR===========> a - CZM0041 The invocation of macro Say contains fewer arguments than are required by the macro definition. <font color="red"><--- What? It seems there HAS to be a variadic argument. Giving none won't work with this compiler<ref>I tried several compiler settings (f.e. LANGLVL), and even using __VA_OPT__.</ref></font>		ERROR===========> a - CZM0041 The invocation of macro Say contains fewer arguments than are required by the macro definition. <font color="red"><--- What? It seems there HAS to be a variadic argument. Giving none won't work with this compiler<ref>I tried several compiler settings (f.e. LANGLVL), and even using __VA_OPT__.</ref></font>
	SEVERE==========> b - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>		SEVERE==========> b - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously, this truncated line misses some characters...</font>

Heiko: /* The Solution */

2019-11-28T10:35:02Z

The Solution

← Older revision		Revision as of 12:35, 28 November 2019
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	35 ! // TEST W/ ADDITIONAL variadic arguments !		35 ! // TEST W/ ADDITIONAL variadic arguments !
	36 ! Say(0, "Error: Socket creation failed with %s\n", "just a random argument");		36 ! Say(0, "Error: Socket creation failed with %s\n", "just a random argument");
	36 + logWithMethodName("connectAMI", 36, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>		36 + logWithMethodName("connectAMI", 36, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>
	SEVERE==========> a - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>		SEVERE==========> a - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>
	SEVERE==========> b - CZM0045 Undeclared identifier paramete. <font color="red"><--- Obviously this truncated identifier won't work...</font>		SEVERE==========> b - CZM0045 Undeclared identifier paramete. <font color="red"><--- Obviously this truncated identifier won't work...</font>
	37 !		37 !
	38 ! // EMPTY variadic arguments		38 ! // EMPTY variadic arguments
	39 ! Say(0, "Error: Socket creation failed...\n");		39 ! Say(0, "Error: Socket creation failed...\n");
	39 + logWithMethodName("connectAMI", 39, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>		39 + logWithMethodName("connectAMI", 39, 0, (paramete; <font color="red"><--- Note the truncated line! (but the ; is there!)</font>
	ERROR===========> a - CZM0041 The invocation of macro Say contains fewer arguments than are required by the macro definition. <font color="red"><--- What? It seems there HAS to be a variadic argument. Giving none won't work with this compiler<ref>I tried several compiler settings (f.e. LANGLVL), and even using __VA_OPT__.</ref></font>		ERROR===========> a - CZM0041 The invocation of macro Say contains fewer arguments than are required by the macro definition. <font color="red"><--- What? It seems there HAS to be a variadic argument. Giving none won't work with this compiler<ref>I tried several compiler settings (f.e. LANGLVL), and even using __VA_OPT__.</ref></font>
	SEVERE==========> b - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>		SEVERE==========> b - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>


	So what next? I couldn't explain why and how the truncation happened (even after many attempts of understanding/solving this issue) and started to follow the only valid lead: The CZM0041 error, even though was only thrown by one of the two lines.		So what next? I couldn't explain why and how the truncation happened (even after many attempts of understanding/solving this issue) and started to follow the only valid lead: The CZM0041 error, even though was only thrown by one of the two lines.

Heiko at 10:32, 28 November 2019

2019-11-28T10:32:45Z

← Older revision		Revision as of 12:32, 28 November 2019
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	}		}

	==~~= What happened =~~==		== The Solution ==
	Looks fine, you say? I'd agree. This code worked for me for years. Then I compiled it on our AS/400...		Looks fine, you say? I'd agree. This code worked for me for years. Then I compiled it on our AS/400...

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	Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.		Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.

	~~== The Solution ==~~

Heiko: /* What happened */

2019-11-28T10:32:01Z

What happened

← Older revision		Revision as of 12:32, 28 November 2019
Line 91:		Line 91:

	So I changed my define from...		So I changed my define from...
			#define Say(logLevel, parameter, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, (parameter), ##__VA_ARGS__);
	...to...		...to...
	#define Say(logLevel, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, __VA_ARGS__);		#define Say(logLevel, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, __VA_ARGS__);
			Meaning, only the logLevel (severity) argument was defined, everything else, including the always following text message, was part of the VA. This way, VA would always include at least one argument.

	== The Solution ==		== The Solution ==

Heiko: /* The code used */

2019-11-28T10:30:19Z

The code used

← Older revision		Revision as of 12:30, 28 November 2019
Line 13:		Line 13:

	This is how the define adds the filename and linenumber:		This is how the define adds the filename and linenumber:
	~~#if (kDebug)~~		#define Say(logLevel, parameter, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, (parameter), ##__VA_ARGS__);
	#define Say(logLevel, parameter, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, (parameter), ##__VA_ARGS__);
	~~#else~~
	~~#define Say(logLevel, parameter, ...) //#define KeinLoggingHeute~~
	~~#endif~~

	This is the actual logging code (you can skip that, it's not relevant, except for the parameters):		This is the actual logging code (you can skip that, it's not relevant, except for the parameters):

Heiko: /* What happened */

2019-11-28T10:30:06Z

What happened

← Older revision		Revision as of 12:30, 28 November 2019
Line 88:		Line 88:
	SEVERE==========> b - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>		SEVERE==========> b - CZM0277 Syntax error: possible missing ')' or ','? <font color="red"><--- Obviously this truncated line misses some characters...</font>

	So what next? I couldn't explain why and how the truncation happened (even after many attempts of understanding/solving this issue) and started to follow the only valid lead: The CZM0041 error.		So what next? I couldn't explain why and how the truncation happened (even after many attempts of understanding/solving this issue) and started to follow the only valid lead: The CZM0041 error, even though was only thrown by one of the two lines.

	[https://en.wikipedia.org/wiki/Variadic_macro Wikipedia] states: ''Both the [C99] and [C++11] standards '''require at least one argument''', but since [C++20] this limitation has been lifted through the __VA_OPT__ functional macro. The __VA_OPT__ macro is replaced by its argument when arguments are present, and omitted otherwise. <font color="green">Common compilers also permit passing zero arguments before this addition, however.</font>''		[https://en.wikipedia.org/wiki/Variadic_macro Wikipedia] states: ''Both the [C99] and [C++11] standards '''require at least one argument''', but since [C++20] this limitation has been lifted through the __VA_OPT__ functional macro. The __VA_OPT__ macro is replaced by its argument when arguments are present, and omitted otherwise. <font color="green">Common compilers also permit passing zero arguments before this addition, however.</font>''

	The <font color="green">green sentence</font> meant, that all previously used compilers permitted zero arguments, but the AS/400's compiler didn't.		The <font color="green">green sentence</font> meant, that all previously used compilers permitted zero arguments, but the AS/400's compiler didn't.

			So I changed my define from...
			...to...
			#define Say(logLevel, ...) logWithMethodName(__FUNCTION__, __LINE__, logLevel, __VA_ARGS__);

	== The Solution ==		== The Solution ==