non*_*one 13 c memory stack-overflow memory-management
编辑在你兴奋之前,最后看到重要的编辑,如果你仍然好奇,这些被报道为:
我一直在尝试一段代码,并惊讶地发现我没有得到堆栈溢出.试图简化我甚至得到的东西:
#include <stdio.h>
int main()
{
int i;
/* 1,500,000,000 x 4 bytes = 6,000,000,000 bytes = 6GB */
int size = 1500000000;
int arr[size];
for (i = 0; i < size; i++) {
arr[i] = 1;
}
printf("first: %d\n", arr[0]);
printf("last: %d\n", arr[size - 1]);
return 0;
}
这使我怀疑我甚至不知道内存管理的基础知识.我认为arr[size]应该轻松分配堆栈和溢出,但它使用我的所有内存和交换并成功完成.我错过了什么？
我试过gcc和clang版本:
gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
Ubuntu clang version 3.0-6ubuntu3 (tags/RELEASE_30/final) (based on LLVM 3.0)
我关闭了优化(-O0)
跑步ulimit -a我得到:
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 29569
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 29569
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
我有4GBram和大约相同数量的交换
(gdb) disassemble main
Dump of assembler code for function main:
0x00000000004004f4 <+0>: push %rbp
0x00000000004004f5 <+1>: mov %rsp,%rbp
0x00000000004004f8 <+4>: push %rbx
0x00000000004004f9 <+5>: sub $0x38,%rsp
0x00000000004004fd <+9>: mov %rsp,%rax
0x0000000000400500 <+12>: mov %rax,%rbx
0x0000000000400503 <+15>: movl $0x59682f00,-0x14(%rbp)
0x000000000040050a <+22>: mov -0x14(%rbp),%eax
0x000000000040050d <+25>: movslq %eax,%rdx
0x0000000000400510 <+28>: sub $0x1,%rdx
0x0000000000400514 <+32>: mov %rdx,-0x28(%rbp)
0x0000000000400518 <+36>: cltq
0x000000000040051a <+38>: shl $0x2,%rax
0x000000000040051e <+42>: lea 0xf(%rax),%rdx
0x0000000000400522 <+46>: mov $0x10,%eax
0x0000000000400527 <+51>: sub $0x1,%rax
0x000000000040052b <+55>: add %rdx,%rax
0x000000000040052e <+58>: movq $0x10,-0x38(%rbp)
0x0000000000400536 <+66>: mov $0x0,%edx
0x000000000040053b <+71>: divq -0x38(%rbp)
0x000000000040053f <+75>: imul $0x10,%rax,%rax
0x0000000000400543 <+79>: sub %rax,%rsp
0x0000000000400546 <+82>: mov %rsp,%rax
0x0000000000400549 <+85>: add $0xf,%rax
0x000000000040054d <+89>: shr $0x4,%rax
0x0000000000400551 <+93>: shl $0x4,%rax
0x0000000000400555 <+97>: mov %rax,-0x20(%rbp)
0x0000000000400559 <+101>: movl $0x0,-0x18(%rbp)
0x0000000000400560 <+108>: jmp 0x400577 <main+131>
0x0000000000400562 <+110>: mov -0x20(%rbp),%rax
0x0000000000400566 <+114>: mov -0x18(%rbp),%edx
0x0000000000400569 <+117>: movslq %edx,%rdx
0x000000000040056c <+120>: movl $0x1,(%rax,%rdx,4)
0x0000000000400573 <+127>: addl $0x1,-0x18(%rbp)
0x0000000000400577 <+131>: mov -0x18(%rbp),%eax
0x000000000040057a <+134>: cmp -0x14(%rbp),%eax
0x000000000040057d <+137>: jl 0x400562 <main+110>
0x000000000040057f <+139>: mov -0x20(%rbp),%rax
0x0000000000400583 <+143>: mov (%rax),%edx
0x0000000000400585 <+145>: mov $0x4006bc,%eax
0x000000000040058a <+150>: mov %edx,%esi
0x000000000040058c <+152>: mov %rax,%rdi
0x000000000040058f <+155>: mov $0x0,%eax
---Type <return> to continue, or q <return> to quit---
0x0000000000400594 <+160>: callq 0x4003f0 <printf@plt>
0x0000000000400599 <+165>: mov -0x14(%rbp),%eax
0x000000000040059c <+168>: lea -0x1(%rax),%edx
0x000000000040059f <+171>: mov -0x20(%rbp),%rax
0x00000000004005a3 <+175>: movslq %edx,%rdx
0x00000000004005a6 <+178>: mov (%rax,%rdx,4),%edx
0x00000000004005a9 <+181>: mov $0x4006c7,%eax
0x00000000004005ae <+186>: mov %edx,%esi
0x00000000004005b0 <+188>: mov %rax,%rdi
0x00000000004005b3 <+191>: mov $0x0,%eax
0x00000000004005b8 <+196>: callq 0x4003f0 <printf@plt>
0x00000000004005bd <+201>: mov $0x0,%eax
0x00000000004005c2 <+206>: mov %rbx,%rsp
0x00000000004005c5 <+209>: mov -0x8(%rbp),%rbx
0x00000000004005c9 <+213>: leaveq
0x00000000004005ca <+214>: retq
End of assembler dump.
$ pmap 2840
2840: ./a.out
0000000000400000 4K r-x-- /home/gokce/play/a.out
0000000000600000 4K r---- /home/gokce/play/a.out
0000000000601000 4K rw--- /home/gokce/play/a.out
00002b572d7be000 136K r-x-- /lib/x86_64-linux-gnu/ld-2.15.so
00002b572d7e0000 8K rw--- [ anon ]
00002b572d9e0000 4K r---- /lib/x86_64-linux-gnu/ld-2.15.so
00002b572d9e1000 8K rw--- /lib/x86_64-linux-gnu/ld-2.15.so
00002b572d9e3000 1748K r-x-- /lib/x86_64-linux-gnu/libc-2.15.so
00002b572db98000 2044K ----- /lib/x86_64-linux-gnu/libc-2.15.so
00002b572dd97000 16K r---- /lib/x86_64-linux-gnu/libc-2.15.so
00002b572dd9b000 8K rw--- /lib/x86_64-linux-gnu/libc-2.15.so
00002b572dd9d000 28K rw--- [ anon ]
00007ffe080a2000 5859388K rw--- [ stack ]
00007fff6dbfc000 4K r-x-- [ anon ]
ffffffffff600000 4K r-x-- [ anon ]
total 5863408K
重要编辑
我用的是一个小手写的makefile:
build:
gcc foo.c -Wall -Wextra -g
run:
./a.out
.SILENT:
使用我的常用编辑器镜头来运行程序,我现在意识到它在某种程度上是相关的.当我从控制台运行时,我得到了段错误:
./a.out
但不是我跑的时候:
make run
那有什么关系？
重要的编辑2
当我尝试运行ulimit -s时make run:
build:
gcc foo.c -Wall -Wextra -g
run:
ulimit -s
.SILENT:
它给:
make: ulimit: Command not found
make: *** [run] Error 127
然后我意识到当我最后添加一个额外的东西时它会改变#:(不是评论字符吗？)
build:
gcc foo.c -Wall -Wextra -g
run:
ulimit -s #
.SILENT:
我明白了:
unlimited
我还检查了我的bash别名,但没有make.which make给出/usr/bin/make并file /usr/bin/make给出:
/usr/bin/make: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically
linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=0x1d76b881b71091d
37e6653d7c8b8e19a2a414591, stripped
arr正如您所期望的，显然是在堆栈上分配的。从pmap输出来看，堆栈明显增长到接近 6GB：
00007ffe080a2000 5859388K rw--- [ stack ]
因此，问题不在于您的程序或编译器。问题是为什么ulimit -s 8192显然没有得到执行。
从您对我的各种问题的回答来看，很明显，该ulimit -s设置没有从您的 shell 传播make run到您的程序。这对我来说似乎很奇怪。
如果我处于您的位置，我会仔细检查系统limits.conf以及共享和用户的bash启动文件，看看是否可以发现任何相关的内容。