在malloc.c中的SIGABRT,刚刚发生了什么？

Question

我写了这段无辜的代码,导致了这样一个邪恶的错误:

static char * prefixed( char * pref, char *str ) {
    size_t newalloc_size = sizeof(char) * (strlen(pref) + strlen(str));
    char * result = (char*) malloc( newalloc_size );
    [...]

debug(cgdb)的输出:

Breakpoint 1, prefixed (pref=0x401345 "Env: ", str=0x4012b5 "Home") at ./src/backend/os/env.c:77
(gdb) s
(gdb) p newalloc_size 
$1 = 9
(gdb) s
envtest: malloc.c:2368: sysmalloc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >=
(unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)'
failed.

Program received signal SIGABRT, Aborted.
0x00007ffff7a68fd5 in raise () from /usr/lib/libc.so.6
(gdb)  

我也检查了传递的参数.它们就像它们应该是:

Breakpoint 1, prefixed (pref=0x401345 "Env: ", str=0x4012b5 "Home") at ./src/backend/os/env.c:77
(gdb) p pref
$2 = 0x401345 "Env: "
(gdb) p strlen(pref)
$3 = 5
(gdb) p str
$4 = 0x4012b5 "Home"
(gdb) p strlen(str)
$5 = 4
(gdb) 

任何人都可以想象,这里出了什么问题？我知道有两个功能可以将两个字符串组合在一起,但我想自己做!

亲切的问候.

Answer 1

这有点像程序中其他地方的内存泄漏或缓冲区溢出(或其他一些堆损坏).我建议使用-Wall -g选项重新编译它gcc,改进程序,直到编译器没有给出警告,并使用valgrind并gdb调试问题.

实际上,你的陈述

  result = (char*) malloc( newalloc_size );

是错误的(终止空字节的空间不足).你可能想要

  result = malloc(newalloc_size+1);

但你应该学习使用asprintf