c99

问题 I have to define constants like this : #define MY_CONSTANT 0xBEEF I want to be sure that my constant will be considered 32 bits. I have can use a (uint32_t) cast like this : #define MY_CONSTANT (uint32_t)0xBEEF Or a UL suffix like this : #define MY_CONSTANT 0xBEEFUL Are these two versions fully equivalent? I would say no, as UL is the equivalent of unsigned long and unsigned long length may depend on CPU. The C99 standard ensures that an uint32_t integer is 32 bits, but I don't think it

问题 I have to define constants like this : #define MY_CONSTANT 0xBEEF I want to be sure that my constant will be considered 32 bits. I have can use a (uint32_t) cast like this : #define MY_CONSTANT (uint32_t)0xBEEF Or a UL suffix like this : #define MY_CONSTANT 0xBEEFUL Are these two versions fully equivalent? I would say no, as UL is the equivalent of unsigned long and unsigned long length may depend on CPU. The C99 standard ensures that an uint32_t integer is 32 bits, but I don't think it

问题 This question already has answers here : Can sizeof(int) ever be 1 on a hosted implementation? (8 answers) Closed 5 years ago . According to the C standard, any characters returned by fgetc are returned in the form of unsigned char values, "converted to an int " (that quote comes from the C standard, stating that there is indeed a conversion). When sizeof (int) == 1 , many unsigned char values are outside of range. It is thus possible that some of those unsigned char values might end up being

问题 Update Turnes out my lecturer will accept code written to the GNU99 standard, so, as User1 pointed out, I used _GNU_SOURCE at the beginning of my program. (See man feature_test_macros for more info.) Thanks for helping me understand! On Ubuntu 13.10 with Clang 3.4, GCC 4.8.1, I am doing an assignment which requires me to use the C99 standard. (I also have GNUstep installed from SVN) WRT GCC, I think I have 4 versions installed in these folders: /usr/lib/gcc/x86_64-linux-gnu/4.7 /usr/lib/gcc

问题 I have this function: #include <complex.h> complex double f(complex double x, complex double y) { return x*y; } I would like to call it with x = inf + i inf and y = i inf and see what the result is. In particular I want to test if the result is an infinity value (as it should be) or if it is NaN + iNaN . The reason for this is to test different C compilers. How do you do this in C? 回答1: I would add an intermediate check, too: #include <stdio.h> #include <stdlib.h> #include <complex.h>

问题 As per the C99 standard: 6.3.1.8.2 : The values of floating operands and of the results of floating expressions may be represented in greater precision and range than that required by the type; the types are not changed thereby.52)> However, outside the scope of Annex F, we have: 5.2.4.2.2.7 : The values of operations with floating operands and values subject to the usual arithmetic conversions and of floating constants are evaluated to a format whose range and precision may be greater than

问题 As per the C99 standard: 6.3.1.8.2 : The values of floating operands and of the results of floating expressions may be represented in greater precision and range than that required by the type; the types are not changed thereby.52)> However, outside the scope of Annex F, we have: 5.2.4.2.2.7 : The values of operations with floating operands and values subject to the usual arithmetic conversions and of floating constants are evaluated to a format whose range and precision may be greater than

问题 Section 6.8.1 of C11 or C99, or section 3.6.1 of C89 all seem to indicate that default and case x (where x is some constant-expression ) are examples of labeled statements, along-side identifier: -style labels that are suitable for use with goto . I'm aware that I could simply place an identifier: -style label directly following the default: or case x: labels. That's not what this question is about. I'm more curious as to whether there is any actual rationale behind prohibiting this kind of

问题 Section 6.8.1 of C11 or C99, or section 3.6.1 of C89 all seem to indicate that default and case x (where x is some constant-expression ) are examples of labeled statements, along-side identifier: -style labels that are suitable for use with goto . I'm aware that I could simply place an identifier: -style label directly following the default: or case x: labels. That's not what this question is about. I'm more curious as to whether there is any actual rationale behind prohibiting this kind of

问题 Section 6.8.1 of C11 or C99, or section 3.6.1 of C89 all seem to indicate that default and case x (where x is some constant-expression ) are examples of labeled statements, along-side identifier: -style labels that are suitable for use with goto . I'm aware that I could simply place an identifier: -style label directly following the default: or case x: labels. That's not what this question is about. I'm more curious as to whether there is any actual rationale behind prohibiting this kind of