The Short Answer Yes. Common conventions of using FAMs expose our programs to the possibility of undefined behavior. Having said that, I’m unaware of any existing conforming implementation that would misbehave. Possible, but unlikely. Even if we don’t actually reach undefined behavior, we are still likely to fail strict conformance. No. The offset of the … Read more
No, flexible arrays must always be allocated manually. But you may use calloc to initialize the flexible part and a compound literal to initialize the fixed part. I’d wrap that in an allocation inline function like this: typedef struct person { unsigned age; char sex; size_t size; char name[]; } person; inline person* alloc_person(int a, … Read more
This is a way to have variable sizes of data, without having to call malloc (kmalloc in this case) twice. You would use it like this: struct bts_action *var = kmalloc(sizeof(*var) + extra, GFP_KERNEL); This used to be not standard and was considered a hack (as Aniket said), but it was standardized in C99. The … Read more
The [] is a flexible array member. They do not count towards the total size of the struct, because the C standard explicitly says so: 6.7.2.1/18 As a special case, the last element of a structure with more than one named member may have an incomplete array type; this is called a flexible array member. … Read more
Yes this is a C-Hack. To create an array of any length: struct someData* mallocSomeData(int size) { struct someData* result = (struct someData*)malloc(sizeof(struct someData) + size * sizeof(BYTE)); if (result) { result->nData = size; } return result; } Now you have an object of someData with an array of a specified length.
C++ was first standardized in 1998, so it predates the addition of flexible array members to C (which was new in C99). There was a corrigendum to C++ in 2003, but that didn’t add any relevant new features. The next revision of C++ (C++2b) is still under development, and it seems flexible array members still … Read more
It is an accepted “fact” that using goto is poor software engineering practice. That doesn’t make it true. There are times when goto is useful, particularly when handling cleanup and when porting from assembler. Flexible array members strike me as having one main use, off the top of my head, which is mapping legacy data … Read more