c89

问题 To be truly standards-compliant, must all functions in C (except for main) have a prototype, even if they are only used after their definition in the same translation unit? 回答1: It depends on what you mean by 'truly standards compliant'. However, the short answer is "it is a good idea to ensure that all functions have a prototype in scope before being used". A more qualified answer notes that if the function accepts variable arguments (notably the printf() family of functions), then a

问题 To be truly standards-compliant, must all functions in C (except for main) have a prototype, even if they are only used after their definition in the same translation unit? 回答1: It depends on what you mean by 'truly standards compliant'. However, the short answer is "it is a good idea to ensure that all functions have a prototype in scope before being used". A more qualified answer notes that if the function accepts variable arguments (notably the printf() family of functions), then a

问题 To be truly standards-compliant, must all functions in C (except for main) have a prototype, even if they are only used after their definition in the same translation unit? 回答1: It depends on what you mean by 'truly standards compliant'. However, the short answer is "it is a good idea to ensure that all functions have a prototype in scope before being used". A more qualified answer notes that if the function accepts variable arguments (notably the printf() family of functions), then a

问题 I read the 6.3th paragraph of the "C programming language" second edition, by Kernigan & Ritchie. Some structure: struct key { char *word; int count; } keytab[NKEYS] { { "auto", 0 }, { "break", 0 }, { "case", 0 }, { "char", 0 }, { "const", 0 }, { "continue", 0 } }; Authors wrote about it: The quantity NKEYS is the number of keywords in keytab. Although we could count this by hand, it’s a lot easier and safer to do it by machine, especially if the list is subject to change. One possibility

问题 I'm trying to implement a linked list like this: typedef struct SLnode { void* item; void* next; } SLnode; typedef struct DLnode { void* item; void* next; struct DLnode* prev; } DLnode; typedef struct LinkedList { void* head; /*SLnode if doubly_linked is false, otherwise DLnode*/ void* tail; /* here too */ bool doubly_linked; } LinkedList; And I want to access it like this: void* llnode_at(const LinkedList* ll, size_t index) { size_t i; SLnode* current; current = ll->head; for(i = 0; i <

问题 I'm trying to implement a linked list like this: typedef struct SLnode { void* item; void* next; } SLnode; typedef struct DLnode { void* item; void* next; struct DLnode* prev; } DLnode; typedef struct LinkedList { void* head; /*SLnode if doubly_linked is false, otherwise DLnode*/ void* tail; /* here too */ bool doubly_linked; } LinkedList; And I want to access it like this: void* llnode_at(const LinkedList* ll, size_t index) { size_t i; SLnode* current; current = ll->head; for(i = 0; i <

问题 I've tried to search in old questions but I've not solved my problem. I try to explain my doubt; Supposing to work in c89 mode, if there's not a prototype of the function before the function call, there is an implicit declaration of the function, the type of the function is int and the arguments are converted through Default Argument Promotions: the objects of type char or short int (whether signed or not) are promoted to either int or unsigned int, as appropriate; and that objects of type

问题 I am looking for a way to #define a macro that enforces its arguments to be compile time constants, and at the same time can be used in an expression. The method should be working under C90 and be upward compatible - if possible also portable for the different C++ variants. Also a 0-footprint to memory is preferable. Consider a compile-time minimum macro as an example. The behavior should be: #define CT_MIN(CTC_A, CTC B) <<<MAGIC>>> int a = 1; int b = a + CT_MIN(1,4); /* OK */ int c = a + CT

问题 I have some places in my code where I want to assure that a division of 2 arbitrary floating point numbers (32 bit single precision) won't overflow. The target/compiler does not guarantee (explicitly enough) nice handling of -INF/INF and (does not fully guarantees IEEE 754 for the exceptional values - (possibly undefined) - and target might change). Also I cannot make save assumtions on the inputs for this few special places and I am bound to C90 standard libraries. I have read What Every

问题 Some background : the header stdint.h is part of the C standard since C99. It includes typedefs that are ensured to be 8, 16, 32, and 64-bit long integers, both signed and unsigned. This header is not part of the C89 standard, though, and I haven't yet found any straightforward way to ensure that my datatypes have a known length. Getting to the actual topic The following code is how SQLite (written in C89) defines 64-bit integers, but I don't find it convincing. That is, I don't think it's