没有指定类型时，C编译器不引发错误 [英] C Compiler not throwing error when no type is specified

问题描述

为什么这个计划之下不引发错误：

  dfljshfksdhfl;
＃包括LT＆;＆stdio.h中GT;
诠释主（）{
        返回0;
}
 

GCC 也只是抛出一个警告：

  

test.c的：1：1：警告：数据定义没有类型或存储类[默认启用]

解决方案

这是因为即使隐含int是的不再是一部分由于C99 C标准的一些编译器仍然支持它，主要是prevent打破了很多老code的。所以这行：

  dfljshfksdhfl;
 

最后等于为：

  INT dfljshfksdhfl;
 

铛默认情况下为我们带来了更加翔实的警告：

 警告：类型说明符缺少，默认为'廉政'[-Wimplicit-INT]
dfljshfksdhfl;
^ ~~~~~~~~~~~~
 

我们可以使用 -pedantic-错误标志，把它变成一个错误，但奇怪的是，这并不为铛，所以我们不得不诉诸 -Werror 工作，并把所有的警告走入误区，这实际上是一个很好的习惯进入。由于remyabel指出了铛我们还可以使用 = -Werror隐含-INT 。

Why this below program not throwing an error:

dfljshfksdhfl;
#include <stdio.h>
int main () {
        return 0;
}

gcc would just throw a warning:

test.c:1:1: warning: data definition has no type or storage class [enabled by default]

解决方案

This is because even though implicit int is no longer part of the C standard since C99 some compilers still support it, mainly to prevent breaking a lot of old code. So this line:

dfljshfksdhfl;

ends up being equivalent to:

int dfljshfksdhfl;

clang gives us a much more informative warning by default:

warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
dfljshfksdhfl;
^~~~~~~~~~~~~

We can use the -pedantic-errors flag to turn this into an error, although oddly enough this does not work for clang and so we have to resort to -Werror and turn all warnings into errors, which is actually a good habit to get into. As remyabel points out for clang we can also use -Werror=implicit-int.

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