下面的程序可以用gcc編譯，但g++無法編譯。

#include

intmain()

{

foo();//foo() is called before its declaration/definition

}intfoo()

{

printf("Hello");return 0;

}

編譯結果：

diego@ubuntu:~/myProg/geeks4geeks/cpp$ gcc test3.c

diego@ubuntu:~/myProg/geeks4geeks/cpp$ g++test3.c

test3.c: In function'int main()':

test3.c:4:9: error: 'foo' was not declared in thisscope

foo();//foo() is called before its declaration/definition

2) C++中將一個非const指針指向一個const變量是非法的，但在C中是可以的。

#include

int main(void)

{int const j = 20;/*The below assignment is invalid in C++, results in error

In C, the compiler *may* throw a warning, but casting is

implicitly allowed*/

int *ptr = &j; //A normal pointer points to const

printf("*ptr: %d", *ptr);return 0;

}

編譯結果：

diego@ubuntu:~/myProg/geeks4geeks/cpp$ gcc test4.c

test4.c: In function'main':

test4.c:10:16: warning: initialization discards 'const' qualifier from pointer target type [enabled by default]int *ptr = &j; //A normal pointer points to const

^diego@ubuntu:~/myProg/geeks4geeks/cpp$ g++test4.c

test4.c: In function'int main()':

test4.c:10:17: error: invalid conversion from 'const int*' to 'int*' [-fpermissive]int *ptr = &j; //A normal pointer points to const

^

3) C中可以將void* 賦值給其他的指針，如int*， char*等，但是在C++中則需要顯示的類型轉換。

#include

intmain()

{void *vptr;int *iptr = vptr; //In C++, it must be replaced with int *iptr=(int *)vptr;

return 0;

}

編譯結果：

diego@ubuntu:~/myProg/geeks4geeks/cpp$ gcc test5.c

diego@ubuntu:~/myProg/geeks4geeks/cpp$ g++test5.c

test5.c: In function'int main()':

test5.c:5:17: error: invalid conversion from 'void*' to 'int*' [-fpermissive]int *iptr = vptr; //In C++, it must be replaced with int *iptr=(int *)vptr;

這也就意味著在C++中我們調用malloc時需要顯示的轉換類型，“int *p = (void *)malloc(sizeof(int))，而在C中不需要。

4) C++中const變量聲明的同時必須賦初值，但C中不需要賦初值。

#include

intmain()

{const int a; //LINE 4

return 0;

}

編譯結果：

diego@ubuntu:~/myProg/geeks4geeks/cpp$ gcc test6.c

diego@ubuntu:~/myProg/geeks4geeks/cpp$ g++test6.c

test6.c: In function'int main()':

test6.c:4:15: error: uninitialized const 'a' [-fpermissive]const int a; //LINE 4

^

5) C++中的關鍵字在C中不可用，如new，delete，explicit等。

#include

int main(void)

{int new = 5; //new is a keyword in C++, but not in C

printf("%d", new);

}

6) C++有著更加嚴格的類型檢查。C++無法通過編譯，有error，C中僅僅報warning

#include

intmain()

{char *c = 333;

printf("c = %u", c);return 0;

}

編譯結果：

diego@ubuntu:~/myProg/geeks4geeks/cpp$ gcc test7.c

test7.c: In function'main':

test7.c:4:15: warning: initialization makes pointer from integer without a cast [enabled by default]char *c = 333;^test7.c:5:5: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'char *' [-Wformat=]

printf("c = %u", c);^diego@ubuntu:~/myProg/geeks4geeks/cpp$ g++test7.c

test7.c: In function'int main()':

test7.c:4:15: error: invalid conversion from 'int' to 'char*' [-fpermissive]char *c = 333;^test7.c:5:23: warning: format '%u' expects argument of type 'unsigned int', but argument 2 has type 'char*' [-Wformat=]

printf("c = %u", c);^

7) C++變量可以在任意位置定義，但是C中必須是一個語句塊開始的地方。(gcc 中可以編譯。。)

#include

intmain()

{inti;

i=5;

i++;intj;return 0;

}

8) C++存在loop variable，C中不存在。

#include

intmain()

{for(int i=0; i<5; i++)

;return 0;

}

9) C++ main函數必須返回int，C可以返回void

#include

void main (int argc, char *argv[])

{

printf("bye");

}

編譯結果：

diego@ubuntu:~/myProg/geeks4geeks/cpp$ gcc test9.c

diego@ubuntu:~/myProg/geeks4geeks/cpp$ g++test9.c

test9.c:2:34: error: '::main' must return 'int'

void main (int argc, char *argv[])^diego@ubuntu:~/myProg/geeks4geeks/cpp$

總結

以上是生活随笔為你收集整理的c语言编译成功,[C/CPP系列知识] 那些程序C语言可以编译通过但C++无法编译成功 Write a C program that won’t compile in C++...的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。