Hi, Willy
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/* __systry2() is used to select one of two provided low level syscalls */ #define __systry2(a, sys_a, sys_b) \ ((NOLIBC__NR_##a != NOLIBC__NR_NOSYS) ? (sys_a) : (sys_b))But this supposes that all of them are manually defined as you did above. I'd rather implement an ugly is_numeric() macro based on argument resolution. I've done it once in another project, I don't remember precisely where it is but I vaguely remember that it used to check that the string resolution of the argument gave a letter (when it does not exist) or a digit (when it does). I can look into that later if needed. But please avoid extra macro definitions as much as possible, they're a real pain to handle in the code. There's no error when one is missing or has a typo, it's difficult to follow them and they don't appear in the debugger.
Yeah, your reply inspired me to look into the IS_ENABLED() from ../include/linux/kconfig.h macro again, there was a __is_defined() there, let's throw away the ugly sysnr.h. I thought of IS_ENABLED() was only for y/n/m before, but it does return 0 when the macro is not defined, it uses the same trick in syscall() to calculate the number of arguments, if the macro is not defined, then, 0 "argument".
The above trick is only for ""#define something 1" ;-)
BR, Zhangjin