Gcc Error Warning Preprocessor
message. You would use ‘#error’ inside of a conditional that detects a combination of parameters which you know the program does not properly support. For example, if you know that the program will not run properly on a VAX, you might write #ifdef __vax__ #error "Won't work on VAXen. See comments at get_last_object." #endif If you have several configuration parameters that must be set up by the installation in a consistent way, you can use conditionals to detect an inconsistency and report it with ‘#error’. For example, #if !defined(FOO) && defined(BAR) #error "BAR requires FOO." #endif The directive ‘#warning’ is like ‘#error’, but causes the preprocessor to issue a warning and continue preprocessing. The tokens following ‘#warning’ are used as the warning message. You might use ‘#warning’ in obsolete header files, with a message directing the user to the header file which should be used instead. Neither ‘#error’ nor ‘#warning’ macro-expands its argument. Internal whitespace sequences are each replaced with a single space. The line must consist of complete tokens. It is wisest to make the argument of these directives be a single string constant; this avoids problems with apostrophes and the like.
tokens Description #error emits tokens to standard error, and increments the assembler error counter, hereby preventing the program from being successfully assembled. #error is specified in the ANSI C standard. #warning emits tokens to standard error, and increments the assembler warning counter. #warning is not specified in the ANSI C standard, but is commonly implemented in preprocessors such as the GNU C preprocessor. #message emits tokens to standard output, and does not affect assembler error or warning counters. #message is not specified in the ANSI C standard.For all directives, the output will include file name and line number, like normal error and warning messages.tokens is a sequence of preprocessor tokens. https://gcc.gnu.org/onlinedocs/cpp/Diagnostics.html Preprocessor macros are expanded except if appearing inside quoted strings (").Example #error "Unsupported part:" __PART_NAME__ PrevUpNextHomeContentsSearchDocumentation HomeAVR AssemblerPrefaceAVR Assembler Known IssuesAVR Assembler Command Line OptionsAssembler sourceAVR Assembler SyntaxAssembler directivesAVR Assembler PreprocessorIntroductionPreprocessor directives#define#undef#ifdef#ifndef#if and #elif#else#endif#error, #warning and #message#include#pragma, general purpose#pragma , AVR part related# (empty directive)OperatorsStringification (#)Concatenation (##)Pre-defined macrosExpressionsInstruction mnemonicsArithmetic and logic instructionsBranch InstructionsData Transfer InstructionsBit and Bit-test InstructionsI/O RegistersInstruction Set Nomenclature:Instructions ADC - Add with Carry ADD - Add without Carry http://www.atmel.com/webdoc/avrassembler/avrassembler.wb_preprocessor.error.html ADIW - Add Immediate to Word AND - Logical AND ANDI - Logical AND with Immediateand ASR - Arithmetic Shift Right BCLR - Bit Clear in SREG BLD - Bit Load from the T Flag in SREG to a Bit in Register. BRBC - Branch if Bit in SREG is Cleared BRBS - Branch if Bit in SREG is Set BRCC - Branch if Carry Cleared BRCS - Branch if Carry Set BREAK - Break BREQ - Branch if Equal BRGE - Branch if Greater or Equal Signed) BRHC - Branch if Half Carry Flag is Cleared BRHS - Branch if Half Carry Flag is Set BRID - Branch if Global Interrupt is Disabled BRIE - Branch if Global Interrupt is Enabled BRLO - Branch if Lower (Unsigned) BRLT - Branch if Less Than (Signed) BRMI - Branch if Minus BRNE - Branch if Not Equal BRPL - Branch if Plus BRSH - Branch if Same or Higher (Unsigned) BRTC - if the T Flag is Cleared BRTS - Branch if the T Flag is Set BRVC - Branch if Overflow Cleared BRVS - Branch if Overflow Set BSET - Bit Set in SREG BST - Bit Store from Bit in Register to T Flag in SREG CALL - Long Call t
in it's place so we wouldn't lose track of the change.It's easy in gcc. You simply say:#warning FIXME: Code removed because...So that's me sorted for Linux and MacOS. I'm happy in http://goodliffe.blogspot.com/2009/07/c-how-to-say-warning-to-visual-studio-c.html the Fun Place.But in the Dark Place I was clueless. How do you say #warning to Visual Studio? You can happily write #warning in C#, but not C++.Interestingly, the answer fell below my Google/Boredom Threshold (i.e. a web http://www.rowleydownload.co.uk/arm/documentation/gnu/cpp/Pragmas.html search didn't reveal the answer in sufficient few clicks that I lost interest). I just shoved in a run-time assertion instead. It'd do the job, but not as immediately as I would have liked.Thanks to hashpling and gcc error the miracle that is Twitter, I now know the answer, and share it with you in the vein hope it might come higher up the Google rankings for those poor souls that follow me:#pragma message ("FIXME: Code removed because...")Needless to say, this is all tediously non-standard.For bonus pointsThis still doesn't get us exactly the same behaviour as gcc's #warning. The message is produced, but without file and line information. This means that if you double-click gcc error warning the message in the VS IDE it will not jump to the warning in the editor window. It also means that build logs aren't much use.Sam Saariste pointed this out, and here's the standard preprocessor mumbo-jumbo you have to jump through to get the exact warning behaviour I was after:#define STRINGIZE_HELPER(x) #x#define STRINGIZE(x) STRINGIZE_HELPER(x)#define WARNING(desc) message(__FILE__ "(" STRINGIZE(__LINE__) ") : Warning: " #desc)// usage:#pragma WARNING(FIXME: Code removed because...)Couldn't be simpler, could it?! Posted by Pete Goodliffe at 04:00 Labels: c++, code 8 comments: codemonkey_uk said... It's a shame you can't #define a #pragma, or you could take this to it's logical conclusion:#define STRINGIFY(x) #x#define TOSTRING(x) STRINGIFY(x)#define WARNING( txt ) __FILE__"(" TOSTRING(__LINE__) ") : warning: " txt#pragma message( WARNING( "a warning you can click on" ) ) 2 July 2009 at 05:48 Pete Goodliffe said... To be honest, it's a shame there's still no standard way of doing this.#warning seems quite sensible to me... 2 July 2009 at 05:53 James Slaughter said... So the obvious question is: Why do that?I think it's a mistake to use compiler output as your bug tracking tool. We've all seen noisy builds that spew so many diagnostics that new problems are lost in the wash. Either the problem's important enough to fix now, or it should go in the bug database... 4 July 2009 at 05:25 Pete Goodliffe said...
as pragmas ) are specified by the 1999 C standard. A C compiler is free to attach any meaning it likes to other pragmas. GCC has historically preferred to use extensions to the syntax of the language, such as __attribute__ , for this purpose. However, GCC does define a few pragmas of its own. These mostly have effects on the entire translation unit or source file. In GCC version 3, all GNU-defined, supported pragmas have been given a GCC prefix. This is in line with the STDC prefix on all pragmas defined by C99. For backward compatibility, pragmas which were recognized by previous versions are still recognized without the GCC prefix, but that usage is deprecated. Some older pragmas are deprecated in their entirety. They are not recognized with the GCC prefix. See Obsolete Features . C99 introduces the _Pragma operator. This feature addresses a major problem with ‘ #pragma ’: being a directive, it cannot be produced as the result of macro expansion. _Pragma is an operator, much like sizeof or defined , and can be embedded in a macro. Its syntax is _Pragma( string-literal ) , where string-literal can be either a normal or wide-character string literal. It is destringized, by replacing all ‘ \\ ’ with a single ‘ \ ’ and all ‘ \" ’ with a ‘ " ’. The result is then processed as if it had appeared as the right hand side of a ‘ #pragma ’ directive. For example, _Pragma ("GCC dependency \"parse.y\"") has the same effect as #pragma GCC dependency "parse.y" . The same effect could be achieved using macros, for example #define DO_PRAGMA(x) _Pragma (#x) DO_PRAGMA (GCC dependency "parse.y") The standard is unclear on where a _Pragma operator can appear. The preprocessor does not accept it within a preprocessing conditional directive like ‘ #if ’. To be safe, you are probably best keeping it out of directives other than ‘ #define ’, and putting it on a line of its own. This manual documents the pragmas which are meaningful to the preprocessor itself. Other pragmas are meaningful to the C or C++ compilers. They are documented in the GCC manual. GCC plugins may provide their own pragmas. #pragma GCC de