我正在尝试在大内存映射文件中查找正则表达式
通过使用正则执行()功能。我发现当文件大小变大时程序崩溃
是页面大小的倍数。
有没有正则执行()具有字符串长度的函数
作为附加参数?
Or:
如何在内存映射文件中查找正则表达式?
这是总是崩溃的最小示例
(如果我运行少于 3 个线程,程序不会崩溃):
ls -la ttt.txt
-rwx------ 1 bob bob 409600 Jun 14 18:16 ttt.txt
gcc -Wall mal.c -o mal -lpthread -g && ./mal
[1] 11364 segmentation fault (core dumped) ./mal
程序是:
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <stdio.h>
#include <assert.h>
#include <pthread.h>
#include <regex.h>
void* f(void*arg) {
int size = 409600;
int fd = open("ttt.txt", O_RDONLY);
char* text = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
close(fd);
fd = open("/dev/zero", O_RDONLY);
char* end = mmap(text + size, 4096, PROT_READ, MAP_PRIVATE | MAP_FIXED, fd, 0);
close(fd);
assert(text+size == end);
regex_t myre;
regcomp(&myre, "XXXXX", REG_EXTENDED);
regexec(&myre, text, 0, NULL, 0);
regfree(&myre);
return NULL;
}
int main(int argc, char* argv[]) {
int n = 10;
int i;
pthread_t t[n];
for (i = 0; i < n; ++i) {
pthread_create(&t[n], NULL, f, NULL);
}
for (i = 0; i < n; ++i) {
pthread_join(t[n], NULL);
}
return 0;
}
附:
这是 gdb 的输出:
gdb ./mal
GNU gdb (Ubuntu/Linaro 7.4-2012.04-0ubuntu2) 7.4-2012.04
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
Reading symbols from /home/bob/prog/c/mal...done.
(gdb) r
Starting program: /home/srdjan/prog/c/mal
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff77ff700 (LWP 11817)]
[New Thread 0x7ffff6ffe700 (LWP 11818)]
[New Thread 0x7ffff6799700 (LWP 11819)]
[New Thread 0x7fffeffff700 (LWP 11820)]
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff6799700 (LWP 11819)]
__strlen_sse2 () at ../sysdeps/x86_64/multiarch/../strlen.S:72
72 ../sysdeps/x86_64/multiarch/../strlen.S: No such file or directory.
(gdb) bt
#0 __strlen_sse2 () at ../sysdeps/x86_64/multiarch/../strlen.S:72
#1 0x00007ffff78df254 in __regexec (preg=0x7ffff6798e80, string=0x7fffef79b000 'a' <repeats 200 times>..., nmatch=<optimized out>,
pmatch=0x0, eflags=<optimized out>) at regexec.c:245
#2 0x00000000004008e6 in f (arg=0x0) at mal.c:24
#3 0x00007ffff7bc4e9a in start_thread (arg=0x7ffff6799700) at pthread_create.c:308
#4 0x00007ffff78f24bd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#5 0x0000000000000000 in ?? ()
(gdb)