c99

If I've got a pointer to some heap allocated space that represents a typical row-major two dimensional array, is it safe to cast this pointer to an equivalent pointer to a VLA for convenient sub-scripting? Example: // // Assuming 'm' was allocated and initialized something like: // // int *matrix = malloc(sizeof(*matrix) * rows * cols); // // for (int r = 0; r < rows; r++) { // for (int c = 0; c < cols; c++) { // matrix[r * cols + c] = some_value; // } // } // // Is it safe for this function to cast 'm' to a pointer to a VLA? // void print_matrix(int *m, int rows, int cols) { int (*mp)[cols] =

This question already has answers here : Closed 2 years ago . Why doesn't C provide struct comparison? (5 answers) The unavailability of structs as comparison operands is one of the more obvious things in C that don't make too much sense (to me). structs can be passed by value and copied via assignments but == is not specified for them. Below are the relevant parts of the C11 standard (draft) that define the constraints of the equality operators ( == and != ) and the simple assignment operator ( = ). Note the lack of structures and unions in the constraints of equality operators. (Apart from

This question already has answers here : Closed 12 months ago . Why are compound literals in C modifiable (1 answer) Why do I get a segmentation fault when writing to a string initialized with “char *s” but not “char s[]”? (17 answers) Does the C99 standard permit writing to compound literals (structs)? It seems it doesn't provide writing to literal strings. I ask about this because it says in C Programming: A Modern Approach, 2nd Edition on Page 406. Q. Allowing a pointer to a compound literal would seem to make it possible to modify the literal. Is that the case? A. Yes. Compound literals

I'm looking for a table (or a way to generate one) for every character in each of the following C Character Sets: Basic Character Set Basic Execution Character Set Basic Source Character Set Execution Character Set Extended Character Set Source Character Set C99 mentions all six of these under section 5.2.1 . However, I've found it extremely cryptic to read and lacking in detail. The only character sets that it clearly defines is the Basic Execution Character Set and the Basic Source Character Set : 52 upper- and lower-case letters in the Latin alphabet: A B C D E F G H I J K L M N O P Q R S T

I would like to know how a variable length array is managed (what extra variables or data structures are kept on the stack in order to have variable length arrays). Thanks a lot. It's just a dynamically sized array (implementation-dependent, but most commonly on the stack). It's pretty much like alloca in the old days, with the exception that sizeof will return the actual size of the array, which implies that the size of the array must also be stored somewhere (implementation-dependent as well, but probably on the stack too). The size of variable length arrays is determined on run-time,

Thankfully, the complex type modifier was introduced into C99 standard. What I don't understand is why it was decided to omit support for fixed point arithmetic (specifically, support fractional types like 1.15 {signed} or 0.32 {unsigned}) where these types are so fundamental to DSP programming? Does GCC support these through an extension? It's been discussed/proposed (e.g., in N938 , N953 ) but those papers have only proposed it as extensions, not additions to the main standard. Those seem to have led to its inclusion in N1169 , which is a draft of TR 18037 ("Extensions to support embedded

Working in C11, the following struct: struct S { unsigned a : 4; _Bool b : 1; }; Gets layed out by GCC as an unsigned (4 bytes) of which 4 bits are used, followed by a _Bool (4 bytes) of which 1 bit is used, for a total size of 8 bytes. Note that C99 and C11 specifically permit _Bool as a bit-field member. The C11 standard (and probably C99 too) also states under §6.7.2.1 'Structure and union specifiers' ¶11 that: An implementation may allocate any addressable storage unit large enough to hold a bit-field. If enough space remains, a bit-field that immediately follows another bit-field in a