这是由C99标准明确定义的吗？

Question

I've made the linker happy by defining main even though there's no main function in my program. Is this valid by the C99 standard?

void foo()
{
    __asm__ (".globl main\n\n"
        "main:\n"
        "\txorl %eax, %eax\n"
        "\tret");
}

Live example

Answer 1

不，C标准没有定义任何内联汇编的行为。

Answer 2

An implementation may provide __asm__ keyword, but only as an extension . In particular, C99 standard lists asm block within informative (non-normative) section J.5.10 The asm keyword :

The asm keyword may be used to insert assembly language directly into the translator output (6.8). The most common implementation is via a statement of the form:

asm ( character-string-literal );

To be most precise, you program is not strictly conforming. From §4/p5 Conformance (emphasis mine):

A strictly conforming program shall use only those features of the language and library specified in this International Standard. ²⁾

Answer 3

C中没有__asm__关键字，因此使用未在C中定义的关键字的简单事实意味着您的程序不严格符合。