int is a “most efficient type” in speed/size – but that is not specified by per the C spec. It must be 16 or more bits. int_fast16_t is most efficient type in speed with at least the range of a 16 bit int. Example: A given platform may have decided that int should be 32-bit … Read more
This does not answer the originally posed question, but if you are a programmer working with similar issues, this answer might help you. I really don’t see where the perceived difficulty is. Providing strict IEEE-754 binary64 semantics while being limited to 80387 floating-point math, and retaining 80-bit long double computation, seems to follow well-specified C99 … Read more
If the attributes don’t work, or aren’t an option …. I’m not sure, but try this: void vecadd (float * restrict a, float * restrict b, float * restrict c) { a = __builtin_assume_aligned (a, 8); b = __builtin_assume_aligned (b, 8); c = __builtin_assume_aligned (c, 8); for …. That should tell GCC that the pointers … Read more
It’s actually quite common to store a number without needing to know the exact size of the type. There are plenty of quantities in my programs that I can reasonably assume won’t exceed 2 billion, or enforce that they don’t. But that doesn’t mean I need an exact 32 bit type to store them, any … Read more
If you are on windows and using mingw, gcc uses the win32 runtime, where printf needs %I64d for a 64 bit integer. (and %I64u for an unsinged 64 bit integer) For most other platforms you’d use %lld for printing a long long. (and %llu if it’s unsigned). This is standarized in C99. gcc doesn’t come … Read more
No. According to the normative wording of the standard, a definition using empty parentheses without the void keyword is not one of the forms that must be accepted, and strictly speaking the behavior of such a program is undefined. Reference: N1570 section 5.1.2.2.1. (The published 2011 ISO C standard, which is not freely available, has … Read more
In the very beginning of C the available memory and CPU resources were really scarce. So it had to compile really fast with minimal memory requirements. Therefore the C language has been designed to require only a very simple compiler which compiles fast. This in turn lead to “single-pass compiler” concept: The compiler reads the … Read more
Use 3 octal digits: char problem[] = “abc\022e”; or split your string: char problem[] = “abc\x12” “e”; Why these work: Unlike hex escapes, standard defines 3 digits as maximum amount for octal escape. 6.4.4.4 Character constants … octal-escape-sequence: \ octal-digit \ octal-digit octal-digit \ octal-digit octal-digit octal-digit … hexadecimal-escape-sequence: \x hexadecimal-digit hexadecimal-escape-sequence hexadecimal-digit String literal … Read more
C99 C11 introduced compound literals which allow not only a complicated initialized structure, but also an “in-line” variable. Code can call a conversion function and pass in a new buffer (char [UTOA_BASE_N]){0} per each function call allowing the function to return that same buffer, now written as needed that is still within its lifetime. The … Read more
No, fgets is not actually deprecated in C99 or the current standard, C11. But the author of that tutorial is right that fgets will not stop when it encounters a NUL, and has no mechanism for reporting its reading of such a character. The fgets function reads at most one less than the number of … Read more