Merge pull request #275 from CapeLeidokos/ng_pr_macro_helpers
New header src/macro_helpers.h that supports preprocessor-macrospull/308/head
Jesse Vincent
7 years ago
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GitHub
commit
842294af78
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#pragma once
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// Code generated by muli-line pre-processor macros is hard to read after
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// pre-processing.
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//
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// When you want to check pre-processed code, e.g. for debugging or
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// to understand what's going on, do the following:
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//
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// 1) Add the compiler command line definition
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// -DKALEIDOSCOPE_ENABLE_MACRO_NEWLINE_SUBSTITUTION
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// This prevents the __NL__ macro being defined below.
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// 2) Generate the preprocessed code (it will contain a lot of __NL__ definitions).
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// 3) Open the pre-processed code in your favorite editor.
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// 3.1) Replace all __NL__ with newline characters.
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// In vim the command would be ':%s/__NL__/\r/g'.
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// 3.2) Autocorrect code-indenting to improve readability. This is necessary
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// as pre-processor macros remove all whitespaces at the beginning of lines.
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// With vim, the command gg=G helps (just type the characters one after
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// the other).
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// 4) Don't forget to remove the
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// -DKALEIDOSCOPE_ENABLE_MACRO_NEWLINE_SUBSTITUTION
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// from your compiler command line. Else the code won't compile.
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#ifndef KALEIDOSCOPE_ENABLE_MACRO_NEWLINE_SUBSTITUTION
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#define __NL__
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#endif
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#define __NN__
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// Some auxiliary macros
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//
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#define __STRINGIZE(S) #S
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#define STRINGIZE(S) __STRINGIZE(S)
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// Allow for the creation of verbose messages in static_asserts
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//
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#define VERBOSE_STATIC_ASSERT_HEADER \
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__NL__ "\n" \
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__NL__ "\n***************************************************************" \
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__NL__ "\n******************** READ THIS CAREFULLY! *********************" \
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__NL__ "\n***************************************************************" \
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__NL__ "\n"
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#define VERBOSE_STATIC_ASSERT_FOOTER \
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__NL__ "\n" \
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__NL__ "\n***************************************************************" \
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__NL__ "\n***************************************************************" \
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__NL__ "\n***************************************************************" \
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__NL__ "\n"
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#define VERBOSE_FILE_INFO \
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__NL__ "\nFile: " __FILE__
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#define VERBOSE_LINE_INFO \
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__NL__ "\nLine: " STRINGIZE(__LINE__)
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// The macro function RESTRICT_ARGS_COUNT can be used to generate more
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// verbose error messages when users supply an insuitable number of arguments
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// to a macro.
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//
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// For a macro it is used wherever one of the arguments A, B, C might
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// be used, e.g.
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//
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#if 0 // This is just so that A_MACRO is not actually defined
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#define A_MACRO(A, B, C, ...) \
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(void)RESTRICT_ARGS_COUNT(0, 3, A_MACRO, ##__VA_ARGS__); \
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int a = A; \
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int b = B; \
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int c = C;
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#endif
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//
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// Note that RESTRICT_ARGS_COUNT can also be invoked wherever one of the macro
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// arguments is used, e.g.
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//
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#if 0 // This is just so that B_MACRO is not actually defined
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#define B_MACRO(A, B, C, ...)
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int array[] = { A, B, RESTRICT_ARGS_COUNT(C, 3, B_MACRO, ##__VA_ARGS__) };
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#endif
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//
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#define RESTRICT_ARGS_COUNT(B, \
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NUM_EXPECTED_ARGS, \
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ORIGINAL_MACRO, \
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...) \
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__NN__ ( \
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__NL__ []{ /* Here we are in the body of a dummy lambda function. \
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__NN__ []{} is, BTW, the shortest way to write a lambda. \
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__NN__ It is only used to hold the static_assert that cannot be \
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__NN__ defined directly in the keymap initializer list. By using the \
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__NN__ comma operator ((A, B) always evaluates to b), we ensure \
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__NN__ that not the lambda but B is what ASSERT_ARGS_COUNT \
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__NN__ finally evaluates to. \
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__NN__ Please not that passing B through this macro is a must \
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__NN__ as we need it for the comma operator to work. \
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__NN__ */ \
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__NN__ static_assert(sizeof(const char) == sizeof(#__VA_ARGS__ ), \
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__NN__ /* sizeof(const char) == sizeof(#__VA_ARGS__ ) checks the quoted \
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__NN__ list of additional arguments. If there are none, then the \
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__NN__ length of #__VA_ARGS__ is a single char as it contains '\0'. \
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__NN__ This check is not able to find the corner case of a single \
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__NN__ superfluous comma at the end of the macro arguments as this \
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__NN__ causes #__VA_ARGS__ being empty (only '\0'). \
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__NN__ */ \
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__NN__ VERBOSE_STATIC_ASSERT_HEADER \
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__NN__ \
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__NN__ VERBOSE_FILE_INFO \
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__NN__ VERBOSE_LINE_INFO \
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__NL__ "\n" \
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__NL__ "\nStrange arguments encountered in invocation of " #ORIGINAL_MACRO "." \
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__NL__ "\n" \
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__NL__ "\nPlease make sure to pass exactly " #NUM_EXPECTED_ARGS \
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__NN__ " macro arguments to" \
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__NL__ "\n" #ORIGINAL_MACRO ". Also make sure that there are no dangling" \
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__NL__ "\ncommas at the end of the argument list." \
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__NL__ "\n" \
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__NL__ "\nThis is the superfluous part at the end of the macro" \
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__NL__ "\narguments list: \'" #__VA_ARGS__ "\'" \
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__NN__ \
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__NN__ VERBOSE_STATIC_ASSERT_FOOTER \
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__NL__ ); \
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__NL__ \
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__NL__ }, /* End of dummy lambda, the comma operator's A operand. */ \
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__NL__ B /* The overall ASSERT_ARGS_COUNT evaluates to B. */ \
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__NL__ )
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