free()无效的指针 [英] free() invalid pointer

问题描述

我得到了熟悉的free():无效的指针错误.在尝试调试时，我最终逐一注释掉了代码中的每个free()，直到没有剩余的代码为止，并且仍然出现运行时错误.还有其他人遇到类似的问题吗?

I'm getting the familiar free(): invalid pointer error. In trying to debug, I ended up commenting out each free() in my code, one by one, until there were none left and I'm still getting this runtime error. Has anyone else run into a similar issue?

顺便说一句-我很难使用gdb进行调试，因为在打印错误消息时，整个服务器实际上并没有崩溃，而只是处理单个客户端的特定分叉进程.

By the way - it's difficult for me to debug this using gdb, because the entire server doesn't actually crash when the error message is printed, just the particular forked process that was handling the single client.

谢谢.

==============================
*** glibc detected *** ./server: free(): invalid pointer: 0x08641a38 ***
======= Backtrace: =========
/lib/i386-linux-gnu/libc.so.6(+0x6b961)[0xefe961]
/lib/i386-linux-gnu/libc.so.6(+0x6d28b)[0xf0028b]
/lib/i386-linux-gnu/libc.so.6(cfree+0x6d)[0xf0341d]
/usr/lib/i386-linux-gnu/libstdc++.so.6(_ZdlPv+0x21)[0x4c74d1]
./server[0x804b499]
./server[0x804b2ad]
./server[0x804aecd]
./server[0x804ad36]
./server[0x804a3a3]
/lib/i386-linux-gnu/libc.so.6(+0x2fa6f)[0xec2a6f]
/lib/i386-linux-gnu/libc.so.6(+0x2facf)[0xec2acf]
./server[0x804966b]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xe7)[0xea9e37]
./server[0x8049331]
======= Memory map: ========
00338000-00352000 r-xp 00000000 08:01 394236     /lib/i386-linux-gnu/libgcc_s.so.1
00352000-00353000 r--p 00019000 08:01 394236     /lib/i386-linux-gnu/libgcc_s.so.1
00353000-00354000 rw-p 0001a000 08:01 394236     /lib/i386-linux-gnu/libgcc_s.so.1
003c1000-003c2000 r-xp 00000000 00:00 0          [vdso]
0041d000-004fc000 r-xp 00000000 08:01 792946     /usr/lib/i386-linux-gnu/libstdc++.so.6.0.14
004fc000-00500000 r--p 000de000 08:01 792946     /usr/lib/i386-linux-gnu/libstdc++.so.6.0.14
00500000-00501000 rw-p 000e2000 08:01 792946     /usr/lib/i386-linux-gnu/libstdc++.so.6.0.14
00501000-00508000 rw-p 00000000 00:00 0 
00664000-00688000 r-xp 00000000 08:01 394245     /lib/i386-linux-gnu/libm-2.13.so
00688000-00689000 r--p 00023000 08:01 394245     /lib/i386-linux-gnu/libm-2.13.so
00689000-0068a000 rw-p 00024000 08:01 394245     /lib/i386-linux-gnu/libm-2.13.so
00793000-007af000 r-xp 00000000 08:01 394195     /lib/i386-linux-gnu/ld-2.13.so
007af000-007b0000 r--p 0001b000 08:01 394195     /lib/i386-linux-gnu/ld-2.13.so
007b0000-007b1000 rw-p 0001c000 08:01 394195     /lib/i386-linux-gnu/ld-2.13.so
00960000-0096a000 r-xp 00000000 08:01 394254     /lib/i386-linux-gnu/libnss_files-2.13.so
0096a000-0096b000 r--p 00009000 08:01 394254     /lib/i386-linux-gnu/libnss_files-2.13.so
0096b000-0096c000 rw-p 0000a000 08:01 394254     /lib/i386-linux-gnu/libnss_files-2.13.so
00e93000-00fed000 r-xp 00000000 08:01 394208     /lib/i386-linux-gnu/libc-2.13.so
00fed000-00fee000 ---p 0015a000 08:01 394208     /lib/i386-linux-gnu/libc-2.13.so
00fee000-00ff0000 r--p 0015a000 08:01 394208     /lib/i386-linux-gnu/libc-2.13.so
00ff0000-00ff1000 rw-p 0015c000 08:01 394208     /lib/i386-linux-gnu/libc-2.13.so
00ff1000-00ff4000 rw-p 00000000 00:00 0 
08048000-08056000 r-xp 00000000 08:01 1084793    /home/mwrosen/cpe464/prog2/server
08056000-08057000 r--p 0000d000 08:01 1084793    /home/mwrosen/cpe464/prog2/server
08057000-08058000 rw-p 0000e000 08:01 1084793    /home/mwrosen/cpe464/prog2/server
08641000-08662000 rw-p 00000000 00:00 0          [heap]
b7600000-b7621000 rw-p 00000000 00:00 0 
b7621000-b7700000 ---p 00000000 00:00 0 
b7718000-b771b000 rw-p 00000000 00:00 0 
b7729000-b772c000 rw-p 00000000 00:00 0 
bfacf000-bfaf0000 rw-p 00000000 00:00 0          [stack]

推荐答案

尝试使用 valgrind 调试问题

如果即使删除了所有free，错误仍然存​​在，则可能是因为某些代码正在其内存区中溢出(例如，缓冲区溢出).

If your error persist even with all free removed, it could be because some code is overflowing its memory zone (e.g. a buffer overflow).

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