c - 为什么 Visual Studio C 编译器不喜欢这样呢？

Question

以下代码在 Linux 上使用 gcc -std=c99 可以正常编译，但在 Visual Studio 2010 C 编译器上出现以下错误:

Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.40219.01 for 80x86Copyright (C) Microsoft Corporation.  All rights reserved.fib.cfib.c(42) : error C2057: expected constant expressionfib.c(42) : error C2466: cannot allocate an array of constant size 0fib.c(42) : error C2133: 'num' : unknown size

The user inputs the amount of Fibonacci numbers to generate. I'm curious as to why the Microsoft compiler doesn't like this code.

#include <stdlib.h>
#include <stdio.h>
#include <limits.h>

void fib(int max);

int main(int argc, char *argv[])
{    
    int argument;

    if (argc != 2)
    {
        puts("You must supply exactly one command line argument.");
        return 0;
    }

    argument = atoi(argv[1]);

    if (argument == 0)
    {
        puts("You gave us 0 or an invalid integer.");
        return 0;
    }
    else if (argument < 0)
    {
        puts("You gave us a negative integer.");
        return 0;
    }
    else if (argument == INT_MAX)
    {
        puts("You gave us a number that's too big to fit in an integer.");
        return 0;
    }

    printf("%d\n", argument);
    fib(argument);
    return 0;
}

void fib(int max)
{
    int num[max]; /// <- Line 42

    int i;
    for (i = 0; i < max; i++)
    {    
        if (i == 0)
            num[i] = 0;
        else if (i == 1)
            num[i] = 1;
        else
            num[i] = num[i-1] + num[i-2];

        printf("%d\t%d\n", i, num[i]);
    }
}

Answer 1

void fib(int max)
{
    int num[max];

微软的 C 编译器不支持 C99，我相信他们已经说过永远不会支持。这意味着数组只能声明为常量大小。