c99

问题 I read with interest the post "How universally is C99 supported ?". One of the comments therein points that Microsoft doesn't support C99. But the comment symbol // works with VS 2008 and this symbol is in C99. I have two questions: To what extent VS 2008 support C99? Is it ok in the same code to mix C89 and C99 syntax together? So if I write my code in C89 and then place a comment //. This means that I have mixed-coding. So what does the compiler do in such a case? Check my code first with

问题 I've been doing some matrix calculation in C for university the other day where I had a 5x5 matrix to begin with so I hard-coded it into the source. It was a 2D array of doubles like: /** * This is the probability-matrix for reaching from any profile * to another by randomly selecting a friend from the friendlist. */ static const double F[5][5] = { /* P , F , L , A , S */ /* Peter */ {0 , 0.5 , 0.5 , 0 , 0 }, /* Franz */ {1.0 , 0 , 0 , 0 , 0 }, /* Lisa */ {0 , 1/3.0, 0 , 1/3.0, 1/3.0}, /*

问题 How to invoke(call) ".so" file in xcode? these ".so" files are all writen in standard C.(C99). Anyone help..... 回答1: Apple uses the file extension ".dylib" for dynamic libraries. They are very similar to ".so" shared-object libraries used in other Unix-like operating systems, and are a cousin to ".dll" dynamic link libraries on Windows. Most .so libraries are in ELF format (used by Linux and many other POSIX systems) whereas Mac libraries are in Mach-O format. So, they are most definitely

问题 If the contents of a file do not match the format string passed to fscanf , what happens on the next call to fscanf ? Suppose a file contains the following two lines: 9000 pig dog 4 5 2 A program tries to parse the opened file ( fp ) as such: int a = 1, b = 1, c = 1; int x = 1, y = 1, z = 1; fscanf(fp, "%d %d %d", &a, &b, &c); fscanf(fp, "%d %d %d", &x, &y, &z); I suspect that a would now hold 9000 while b and c continue to hold the value 1 -- but what happens to x , y , and z ? Does the C99

问题 I've implemented a circular buffer, and I would like a concise means of updating the buffer pointer while properly handling the wrap-around. Assuming an array of size 10, my first response was something like: size_t ptr = 0; // do some work... p = ++p % 10; Static analysis, as well as gcc -Wall -Wextra , rightly slapped my wrist for unspecified behavior due to a sequence point violation. The obvious fix is something like: p++; p %= 10; However, I was looking for something more concise, (i.e.,

问题 I know how to create a structure array inside a function: typedef struct item { int test; }; void func (void) { int arraysize = 5; item ar[arraysize]; } But how do I to the same when the array is declared globally: typedef struct item { int test; }; item ar[]; void func (void) { int arraysize = 5; // What to here? } 回答1: May be you like this: typedef struct item { int test; }; item *arr; void func (void) { int arraysize = 5; arr = calloc(arraysize,sizeof(item)); // check if arr!=NULL :

问题 When I wrote a question regarding PC-Lint, I had made an assumption that the following initialization is valid in C99. @JoachimPileborg mentioned that it may not be and I haven't been able to find any information that provides a good example one way or another. I know that it compiles and behaves as I expect, I would just like to know for certain that it is proper C99 code. Is this a valid way to initialize the following union in C99? typedef union { struct { unsigned int a : 4; unsigned int

问题 C99 (ISO/IEC 9899:1999) 6.2.6.2/1 Integer types The values of any padding bits are unspecified. 45) A valid (non-trap) object representation of a signed integer type where the sign bit is zero is a valid object representation of the corresponding unsigned type, and shall represent the same value. For any integer type, the object representation where all the bits are zero shall be a representation of the value zero in that type. In the C99 standard, an integer type where all the bits are zero

问题 Suppose I have the following function, which makes use of a variable-length array: void func(int size) { int var1; int arr[size]; int var2; ... } How does the compiler determine the address of var2 ? The only way that I can think of is by placing arr after var1 and var2 . But in that case, what if there were several variable-length arrays? Placing all of them after the "normal" variables would only help resolving the address of the first one. My implicit assumption here is that all the local

问题 I apologize for the possible duplicate (have not been able to find an answer to that): Do we need to ensure that the allocation of a variable-length array has completed successfully? For example: void func(int size) { int arr[size]; if (arr == NULL) { // Exit with a failure } else { // Continue as planned } } It seems obvious that the answer is yes , but the syntax arr == NULL feels a bit unusual. Thanks UPDATE: I admit to the fact that I haven't made sure that the code above even compiles