造成在Mac OS X pclose函数（）Valgrind的错误 [英] Valgrind errors caused by pclose() on Mac OS X

问题描述

我试图 pclose函数时，得到的valgrind错误（）管道$ P $与的popen（）pviously打开。出现在Mac OS X中的错误，但不能在Linux上。请看下面的例子：

 的#include＆LT;＆stdlib.h中GT;
＃包括LT＆;＆stdio.h中GT;诠释主（）{
  FILE * FP;
  焦炭BUF [4096];  如果（！（FP =的popen（LS，R）））
    出口（-1）;  而（的fscanf（FP，％S，BUF）== 1）
    的printf（％S \\ n，BUF）;  pclose函数（FP）;  返回0;
}
 

我得到的是Mac（OS X 10.6.7，Valgrind的版本3.6.0）以下Valgrind的错误，除非我删除函数，pclose（）电话：

  == == 21455条件跳转或移动依赖于未初始化值（S）
== == 21455在0xB1992：pclose函数（在/usr/lib/libSystem.B.dylib）
== == 21455通过0x1F16：主（以./a.out）
== == 21455
== == 21455参数系统调用wait4（PID）包含未初始化的字节
== == 21455在0x504FA：wait4（以/usr/lib/libSystem.B.dylib）
== == 21455通过0x1F16：主（以./a.out）
 

不过，我没有得到任何错误Linux系统与Valgrind的版本3.5.0上。

这是什么可能会导致Mac上的错误任何想法？

更新

打开 - 轨道起源在Valgrind的显示问题的起源可能是在的popen（）调用。得到了同样的事情用gcc 4.2.1和4.5.3。

  == == 4425条件跳转或移动依赖于未初始化值（S）
== == 4425在0xB1992：pclose函数（在/usr/lib/libSystem.B.dylib）
== == 4425通过0x1F18：主（以./a.out）
== == 4425值未初始化是由堆栈分配创建
== == 4425在0xB14C5：popen方法$ UNIX2003（以/usr/lib/libSystem.B.dylib）
== == 4425
== == 4425参数系统调用wait4（PID）包含未初始化的字节
== == 4425在0x504FA：wait4（以/usr/lib/libSystem.B.dylib）
== == 4425通过0x1F18：主（以./a.out）
== == 4425值未初始化是由堆栈分配创建
== == 4425在0xB14C5：popen方法$ UNIX2003（以/usr/lib/libSystem.B.dylib）
 

解决方案

这是很常见的系统库未初始化的字节传递给系统调用。这是不太常​​见的条件跳转依赖于未初始化的价值，但它确实发生（的glibc-2.X.supp在我的Linux版本包含8燮pressions此glibc中）。

由于没有什么可以做的这些错误，无论如何，你应该只燮preSS他们。参见 - 根燮pressions 在Valgrind的文档

I'm getting valgrind errors when attempting to pclose() a pipe previously open with popen(). The errors occur on Mac OS X, but not on Linux. Consider the following example:

#include <stdlib.h>
#include <stdio.h>

int main() {
  FILE *fp;
  char buf[4096];

  if (!(fp = popen("ls", "r")))
    exit(-1);

  while (fscanf(fp, "%s", buf) == 1)
    printf("%s\n", buf);

  pclose(fp);

  return 0;
}

I get the following valgrind errors on a Mac (OS X 10.6.7, valgrind version 3.6.0), except if I remove the pclose() call:

==21455== Conditional jump or move depends on uninitialised value(s)
==21455==    at 0xB1992: pclose (in /usr/lib/libSystem.B.dylib)
==21455==    by 0x1F16: main (in ./a.out)
==21455== 
==21455== Syscall param wait4(pid) contains uninitialised byte(s)
==21455==    at 0x504FA: wait4 (in /usr/lib/libSystem.B.dylib)
==21455==    by 0x1F16: main (in ./a.out)

However, I don't get any errors on a Linux system with valgrind version 3.5.0.

Any ideas on what could be causing the errors on the Mac?

Update

Turning on --track-origins in valgrind shows that the origin of the problem might be in the popen() call. Got the same thing with gcc 4.2.1 and 4.5.3.

==4425== Conditional jump or move depends on uninitialised value(s)
==4425==    at 0xB1992: pclose (in /usr/lib/libSystem.B.dylib)
==4425==    by 0x1F18: main (in ./a.out)
==4425==  Uninitialised value was created by a stack allocation
==4425==    at 0xB14C5: popen$UNIX2003 (in /usr/lib/libSystem.B.dylib)
==4425== 
==4425== Syscall param wait4(pid) contains uninitialised byte(s)
==4425==    at 0x504FA: wait4 (in /usr/lib/libSystem.B.dylib)
==4425==    by 0x1F18: main (in ./a.out)
==4425==  Uninitialised value was created by a stack allocation
==4425==    at 0xB14C5: popen$UNIX2003 (in /usr/lib/libSystem.B.dylib)

解决方案

It is quite common for system libraries to pass uninitialized bytes to system calls. It is less common for conditional jump to depend on uninitialized value, but it does happen (glibc-2.X.supp in my Linux build contains 8 suppressions for this in glibc).

Since there is nothing you can do about these errors anyway, you should just suppress them. See --gen-suppressions in Valgrind docs.

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