C 使用fork（）计算收到的命令行参数的总和时出现问题

我试图根据从命令行收到的一组数字来计算总和，我使用一个名为worker的配套程序来完成计算。如果收到的数字量为奇数，它将在数字量上加一个零，使集合为偶数

这是一种可以理解的程序流程（归功于Alok）：

举个例子可以更清楚地说明这一点：

假设您要添加7个数字：1234567

/协调员1234567

输入=[12345670]

n=len（输入）=8

m=n/2=4

输出=[0]

我们分叉4个进程，第一个进程得到[12]，第二个进程得到[34]

这4个进程分别返回3、7、11、7，我们将其分配给输出

输出有4个元素，因此我们为新输入分配了4+1=5个元素的空间

设置输入=[3 7 11 7 0]

n=len（输入）=5

m=n/2=2

输出=[0]

我们分叉两个进程，第一个得到[37]，第二个得到[11]7

这两个进程返回10，18，我们将其分配给输出

输出有2个元素，因此我们为新输入分配2+1=3个元素的空间

设置输入=[10 18 0]

n=len（输入）=3

m=n/2=1

输出=[0]

我们分叉一个进程，得到[10 18]

进程返回28，我们将其分配给输出

输出有1个元素，所以我们完成了 虽然在这组特殊的数字上，我得到：

Process ID: 15195 
Sum of 1 and 2 is 3 

Process ID: 15196 
Sum of 3 and 4 is 7 

Process ID: 15197 
Sum of 5 and 6 is 11 

Process ID: 15198 
Sum of 7 and 0 is 7 

*** glibc detected *** ./coordinator: free(): invalid next size (fast): 0x080ec048 ***

后面是堆错误列表

我认为我没有正确地重新分配指针的大小，在第一次调用next_step（）之后，我试图将旧输出重定向到新输入。因此，它试图将数据放入内存中没有空间的部分

更新：

@诺曼

这是我收到的输出：

==3585== Memcheck, a memory error detector
==3585== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==3585== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==3585== Command: ./coordinator 1 2 3 4
==3585== 
calc: 2:
input[0]: 1
input[1]: 2
input[2]: 3
input[3]: 4
==3585== Use of uninitialised value of size 4
==3585==    at 0x4076186: ??? (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x4079A81: vfprintf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x4080F7F: printf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x8048833: main (in /home/bryan/cpp/coordinator)
==3585== 
==3585== Conditional jump or move depends on uninitialised value(s)
==3585==    at 0x407618E: ??? (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x4079A81: vfprintf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x4080F7F: printf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x8048833: main (in /home/bryan/cpp/coordinator)
==3585== 
==3585== Conditional jump or move depends on uninitialised value(s)
==3585==    at 0x4077877: vfprintf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x4080F7F: printf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x8048833: main (in /home/bryan/cpp/coordinator)
==3585== 
==3585== Conditional jump or move depends on uninitialised value(s)
==3585==    at 0x407789B: vfprintf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x4080F7F: printf (in /lib/tls/i686/cmov/libc-2.10.1.so)
==3585==    by 0x8048833: main (in /home/bryan/cpp/coordinator)
==3585== 
input[4]: 0
==3586== Memcheck, a memory error detector
==3586== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==3586== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==3586== Command: ./worker 1 2
==3586== 
Process ID: 3586 
Sum of 1 and 2 is 3 

==3586== 
==3586== HEAP SUMMARY:
==3586==     in use at exit: 0 bytes in 0 blocks
==3586==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3586== 
==3586== All heap blocks were freed -- no leaks are possible
==3586== 
==3586== For counts of detected and suppressed errors, rerun with: -v
==3586== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 11 from 6)
==3587== Memcheck, a memory error detector
==3587== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==3587== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==3587== Command: ./worker 3 4
==3587== 
Process ID: 3587 
Sum of 3 and 4 is 7 

==3587== 
==3587== HEAP SUMMARY:
==3587==     in use at exit: 0 bytes in 0 blocks
==3587==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3587== 
==3587== All heap blocks were freed -- no leaks are possible
==3587== 
==3587== For counts of detected and suppressed errors, rerun with: -v
==3587== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 11 from 6)
==3585== Invalid write of size 4
==3585==    at 0x8048A3A: main (in /home/bryan/cpp/coordinator)
==3585==  Address 0x417f0b4 is 8 bytes after a block of size 4 alloc'd
==3585==    at 0x4024C6C: malloc (vg_replace_malloc.c:195)
==3585==    by 0x4024CF6: realloc (vg_replace_malloc.c:476)
==3585==    by 0x8048A25: main (in /home/bryan/cpp/coordinator)
==3585== 
==3588== Memcheck, a memory error detector
==3588== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==3588== Using Valgrind-3.5.0 and LibVEX; rerun with -h for copyright info
==3588== Command: ./worker 3 7
==3588== 
Process ID: 3588 
Sum of 3 and 7 is 10 

==3588== 
==3588== HEAP SUMMARY:
==3588==     in use at exit: 0 bytes in 0 blocks
==3588==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3588== 
==3588== All heap blocks were freed -- no leaks are possible
==3588== 
==3588== For counts of detected and suppressed errors, rerun with: -v
==3588== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 11 from 6)
==3585== Invalid read of size 4
==3585==    at 0x8048AB5: main (in /home/bryan/cpp/coordinator)
==3585==  Address 0x417f0e0 is 0 bytes after a block of size 0 alloc'd
==3585==    at 0x4024C6C: malloc (vg_replace_malloc.c:195)
==3585==    by 0x4024CF6: realloc (vg_replace_malloc.c:476)
==3585==    by 0x8048A77: main (in /home/bryan/cpp/coordinator)
==3585== 
The final sum is: 0==3585== 
==3585== HEAP SUMMARY:
==3585==     in use at exit: 28 bytes in 2 blocks
==3585==   total heap usage: 4 allocs, 2 frees, 32 bytes allocated
==3585== 
==3585== LEAK SUMMARY:
==3585==    definitely lost: 8 bytes in 1 blocks
==3585==    indirectly lost: 0 bytes in 0 blocks
==3585==      possibly lost: 20 bytes in 1 blocks
==3585==    still reachable: 0 bytes in 0 blocks
==3585==         suppressed: 0 bytes in 0 blocks
==3585== Rerun with --leak-check=full to see details of leaked memory
==3585== 
==3585== For counts of detected and suppressed errors, rerun with: -v
==3585== Use --track-origins=yes to see where uninitialised values come from
==3585== ERROR SUMMARY: 6 errors from 6 contexts (suppressed: 11 from 6)

---

如果要更改指针，请尝试此操作

无效更改指针（int**输入，int**输出）

及

---

变更指针（输入和输出）

Ray，如果没有看到错误的更多细节，就很难知道出了什么问题。如果，正如我所怀疑的，这些都是运行时错误，您可以在下面运行代码吗

valgrind

在精确定位内存错误方面非常有效；使用您的应用程序，您将需要

valgrind --trace-children=yes ./coordinator 1 2 3 4

编辑：好的，通过valgrind错误，我们可以看到（a）您正在向

printf

传递一些不可靠的东西（如果您使用

-g

编译，您将获得准确的行号），并且您正在调用

realloc

，但不是在

malloc

返回的指针上。也许你做过一些指针运算

---

如果不看代码，就不能说更多，但我希望valgrind对您有所帮助。

您有几个错误：

for（i=0；i

while（计算>0）

---

您应该考虑编写一个函数，让我们将其称为

step_once（）

，它将使用

n

数字执行

input

，并使用

m=n/2

元素写入相应的

output

<上面的code>n是输入数字的数目+1，

input

的最后一个元素等于0

在驱动程序函数中，假设

main（）

：如果

output

包含1个数字，则完成。否则，您将重新分配

input

以包含

n_new=m+1

元素，重新分配

output

以包含

m_new=n_new/2

元素，并再次调用函数

step_（）。你一直这样做直到你得到一个号码：

function next_step(input, output, n, m):
    n := number of input numbers # this is 1 greater than
                                 # the number of numbers being summed
    m := n / 2 # C division
    n_children := m
    i := 0
    while i < m:
        fork worker with input[2*i] and input[2*i+1]
        get result in output[i]
        i := i + 1

function main:
    set n := length(input) + 1
    set m := n/2
    allocate memory for input # n+1 elements, last = 0
    allocate memory for output # m elements
    set values in input
    while True:
        next_step(input, output, n, m)
        if length or output == 1:
             done, return
        else:
            set n := length(output) + 1
            set m := n/2
            allocate space for new_input # n elements
            set new_input := output + [0]
            free input and output
            set input := new_input
            allocate memory for output # m elements

下一步功能（输入、输出、n、m）：
n:=输入数#大于1
#要求和的数字的数目
m:=n/2#C分部
n_儿童：=m
i:=0
而我

优点是，您可以测试

next_step（）

函数，以确保它工作正常，从而使调试更容易

举个例子可以更清楚地说明这一点：

假设您要添加7个数字：1234567

输入

=[1 2 3 4 5 6 7 0]

n

=len（

input

）=8

m

=

n/2

=4

输出

=[0]

我们分叉4个进程，第一个进程得到[12]，第二个进程得到[34]

这4个进程分别返回3、7、11、7，我们将其分配给

输出

output

有4个元素，因此我们为新的

输入分配了4+1=5个元素的空间

设置

输入
=[3 7 11 7 0]

n

=len（

input

）=5

m

=

n/2

=2

输出

=[0]

我们分叉两个进程，第一个得到[37]，第二个得到[11]7

这两个进程返回10、18，我们将其分配给

输出

输出

有2个元素，因此我们为新的

输入

分配了2+1=3个元素的空间

设置

输入
=[10 18 0]

n

=len（

input

）=3