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Crt0 - 版本历史
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<p><b>新页面</b></p><div>{{noteTA|G1=IT}}<br />
{{For|线路代码为CRT0的轨道交通线路|重慶軌道交通環線}}<br />
{{Program execution}}<br />
'''<tt>crt0</tt>'''（也叫做'''<tt>c0</tt>'''）是[[链接器|连接]]到[[C语言|C]]程序上的一组执行启动例程，它进行在调用这个程序的[[主函数]]之前所需要的任何初始化工作。它一般的都采用叫做<tt>crt0.o</tt>的[[目标文件]]形式，经常采用[[汇编语言]]编写，[[链接器]]自动的将它包括入它所建造的所有[[可执行文件]]中<ref name="embecosm">{{cite web<br />
| url = http://www.embecosm.com/appnotes/ean9/html/ch05s02.html<br />
| title = The C Runtime Initialization, crt0.o<br />
| year = 2010<br />
| accessdate = 2013-12-30<br />
| website = embecosm.com<br />
| archive-date = 2013-12-30<br />
| archive-url = https://web.archive.org/web/20131230234426/http://www.embecosm.com/appnotes/ean9/html/ch05s02.html<br />
| dead-url = yes<br />
}}</ref>。<br />
<br />
==简介==<br />
<tt>crt0</tt>包含大多数[[运行时库]]的基本部分。因此，它进行的确切工作依赖于程序的编译器、操作系统和[[C标准库]]实现<ref name="embecosm" />。除了运行时环境和[[工具链]]所需要的初始化工作，<tt>crt</tt>可以进行编程者定义额外操作，比如执行[[C++]]全局[[构造器]]和携带[[GCC]]的<code>((constructor))</code>属性的C函数<ref>{{cite web<br />
| url = http://wiki.osdev.org/Creating_a_C_Library#Program_Initialization<br />
| title = Program initialization: Creating a C library<br />
| date = 2014-02-25<br />
| accessdate = 2014-04-21<br />
| website = osdev.org<br />
| archive-date = 2014-04-23<br />
| archive-url = https://web.archive.org/web/20140423065714/http://wiki.osdev.org/Creating_a_C_Library#Program_Initialization<br />
| dead-url = yes<br />
}}</ref><ref>{{cite web<br />
| url = http://wiki.osdev.org/Calling_Global_Constructors<br />
| title = Calling Global Constructors<br />
| date = 2014-04-08<br />
| accessdate = 2014-04-21<br />
| website = osdev.org<br />
| archive-date = 2014-04-23<br />
| archive-url = https://web.archive.org/web/20140423061748/http://wiki.osdev.org/Calling_Global_Constructors<br />
| dead-url = yes<br />
}}</ref>。<br />
<br />
“crt”表示“C runtime”，“0”表示“最开始”。然而，当程序使用GCC来编译的时候，它也用于在C之外的语言，对于特殊使用场景可获得<tt>crt0</tt>的可替代版本，例如，分析器[[gprof]]要求它的程序同<tt>gcrt0</tt>一起编译<ref>{{cite web<br />
| url = http://sourceware.org/binutils/docs-2.16/gprof/Compiling.html<br />
| title = Compiling a Program for Profiling: GNU gprof<br />
| accessdate = 2013-12-30<br />
| website = sourceware.org<br />
| archive-date = 2013-12-31<br />
| archive-url = https://web.archive.org/web/20131231083357/http://sourceware.org/binutils/docs-2.16/gprof/Compiling.html<br />
| dead-url = yes<br />
}}</ref>。<br />
<br />
== 样例 crt0.s ==<br />
下面是针对[[linux]] [[x86_64]]的采用at&t语法的例子。<br />
<syntaxhighlight lang="asm"><br />
.text<br />
<br />
.globl _start<br />
<br />
_start: # _start is the entry point known to the linker<br />
xor %ebp, %ebp # effectively RBP := 0, mark the end of stack frames<br />
mov (%rsp), %edi # get argc from the stack (implicitly zero-extended to 64-bit)<br />
lea 8(%rsp), %rsi # take the address of argv from the stack<br />
lea 16(%rsp,%rdi,8), %rdx # take the address of envp from the stack<br />
xor %eax, %eax # per ABI and compatibility with icc<br />
call main # %edi, %rsi, %rdx are the three args (of which first two are C standard) to main<br />
<br />
mov %eax, %edi # transfer the return of main to the first argument of _exit<br />
xor %eax, %eax # per ABI and compatibility with icc<br />
call _exit # terminate the program<br />
</syntaxhighlight><br />
<br />
== 参见 ==<br />
* [[入口点]]<br />
* [[运行时系统]]<br />
<br />
== 引用 ==<br />
{{Reflist|2}}<br />
<br />
== 外部链接 ==<br />
* [http://lists.uclibc.org/pipermail/uclibc/2002-December/025943.html crt0.o vs crt1.o]{{Wayback|url=http://lists.uclibc.org/pipermail/uclibc/2002-December/025943.html |date=20180525132542 }}<br />
* [https://dev.gentoo.org/~vapier/crt.txt Mini FAQ about the misc libc/gcc crt files]{{Wayback|url=https://dev.gentoo.org/~vapier/crt.txt |date=20190527141133 }}.<br />
* [http://dbp-consulting.com/tutorials/debugging/linuxProgramStartup.html Linux x86 program start-up]{{Wayback|url=http://dbp-consulting.com/tutorials/debugging/linuxProgramStartup.html |date=20190601190208 }}<br />
* [https://blogs.oracle.com/ksplice/entry/hello_from_a_libc_free Hello from a libc-free world! (Part 1)]{{Wayback|url=https://blogs.oracle.com/ksplice/entry/hello_from_a_libc_free |date=20161117201653 }}, March 16, 2010<br />
<br />
[[Category:C標準函式庫]]</div>
imported>重庆轨交18