是否有一个gcc标志初始化局部变量的存储？ [英] Is there a gcc flag to initialise local variable storage?

问题描述

在IBM AIX XLC 编译器提供了产生code初始化局部变量存储一个标志：

  initauto =＆LT; HH＆GT;
                  Initialialize自动存储到＆lt; HH取代。 ＆LT; HH＆GT;是
                  十六进制值。这会产生额外的code和
                  应仅用于错误判定。
 

我觉得MSVC编译器类似的调试版本，但我的记忆可能是在这一点上朦胧的。

是否有GCC等的选项？

解决方案

确定，最好的答案我可以提供。

<一个href=\"http://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html\">http://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html不作为说不。没有任何东西注入叠擦code到输出文档。

尽可能接近我可以猜测，仅此可能的工作方式，是注入一些 memset的般code（也许那样简单几 MOV 操作，但尽管如此）插入在其中创建一个自动可变每个嵌入词汇帧的开头。由于靠近我可以告诉 - 我的据的从GCC的内部的专家，但是 - 似乎有什么的文件的，会做这样<。 / p>

在进一步在此之后，GCC内幕（http://gcc.gnu.org/onlinedocs/gccint.pdf）的361页的PDF gccint.pdf定义了GCC名入境帧指针调整呼叫步骤一个功能是序言。 （我真的不知道/了解这是否适用于其他词法作用域在函数内，但是。）因为要在一台机器发生定义（MD）的文件，任何这样的选择将的显得的有用于CPU架构中定义。我在他们的在线ViewCVS戳在<一个href=\"http://gcc.gnu.org/viewcvs/trunk/gcc/config/i386/\">http://gcc.gnu.org/viewcvs/trunk/gcc/config/i386/发现（至少一个）序言拷贝各地i386.md的11893线，打搜索换了，功能扩展了几跳后，不似乎有什么东西发出有条件code类的。

但是，这下GCC's罩的东西还挺整齐...

The IBM AIX xlc compiler offers a flag that generates code to initialise local variable storage:

      initauto=<hh>
                  Initialialize automatic storage to <hh>. <hh> is a
                  hexadecimal value.  This generates extra code and
                  should only be used for error determination.

I think the MSVC compiler does something similar for debug builds, but my memory may be hazy on this point.

Is there an equivalent option for GCC?

解决方案

OK, Best answer I can offer.

http://gcc.gnu.org/onlinedocs/gcc/Option-Summary.html says "no," by omission. There's no documentation of anything to inject stack-wiping code into the output.

As near as I could guess, the only way this could work, is to inject some memset-like code (perhaps as simple as a few mov operations, but nonetheless) into the beginning of each embedded lexical frame in which an automatic variable is created. As near as I can tell -- and I am far from an expert on the internals of GCC, but -- there seems to be nothing documented that would do so.

In further following this, the PDF gccint.pdf of GCC Internals (http://gcc.gnu.org/onlinedocs/gccint.pdf) on page 361 defines that the GCC name for the frame pointer adjustment call step on entry to a function is prologue. (I don't really know/understand whether this applies to other lexical scopes within a function, however.) Since that should occur in a Machine Definition (md) file, any such option would seem to have to be defined for a CPU architecture. I poked at their online ViewCVS at http://gcc.gnu.org/viewcvs/trunk/gcc/config/i386/ and found (at least one) copy of prologue around line 11,893 of i386.md, which after playing search-for-the-function-expansion a few hops, doesn't seem to have anything to emit conditional code like that.

But this under-GCC's-hood stuff is kinda neat...

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