SIGSEGV，（貌似）引起的printf [英] SIGSEGV, (seemingly) caused by printf
问题描述
首先，对于任何交叉张贴道歉。希望我不在这里重复的问题，但我无法找到这个在其他地方（通过谷歌和堆栈溢出）。
First and foremost, apologies for any cross-posting. Hope I'm not repeating an issue here, but I was unable to find this elsewhere (via Google and Stack Overflow).
下面是错误的要点。如果我称之为的printf ，的sprintf 或 fprintf中内的任何地方我code，显示一个浮动，我得到一个 SIGSEGV（EXC_BAD_ACCESS）错误。让我举一个例子。
Here's the gist of the error. If I call printf, sprintf or fprintf anywhere within my code, to display a float, I get a SIGSEGV (EXC_BAD_ACCESS) error. Let me give an example.
以下引发错误：
float f = 0.5f;
printf("%f\n",f);
这code不：
float f = 0.5f;
printf("%d\n",f);
我知道有一个隐式转换存在，但我不担心这一点。我只是无法捉摸，为什么打印float与打印整数会抛出一个错误。
I realize there's an implicit conversion there, but I'm not concerned with that. I just can't fathom why printing a float vs. printing an integer would throw an error.
注意：的code使用的部分的malloc 以创建一些非常大的多维数组。然而，这些阵列的不可以以任何方式对这些打印语句被引用。下面是我如何宣布这些阵列的例子。
Note: Part of the code uses malloc to create some very large multidimensional arrays. However, these arrays are not being referenced in any way for these print statements. Here's an example how I'm declaring these arrays.
#define X_LEN 20
#define XDOT_LEN 20
#define THETA_LEN 20
#define THETADOT_LEN 20
#define NUM_STATES (X_LEN+1) * (XDOT_LEN+1) * (THETA_LEN+1) * (THETADOT_LEN+1)
#define NUM_ACTS 100
float *states = (float *)malloc(NUM_STATES * sizeof(float));
// as opposed to float states[NUM_STATES] (more memory effecient)
float **q = (float**)malloc(NUM_STATES * sizeof(float*));
for(int i=0; i < NUM_STATES; i++) {
float *a = (float*)malloc(NUM_ACTS * sizeof(float));
for(int j=0; j < NUM_ACTS; j++) {
a[j] = 0.0f;
}
q[i] = a;
}
和则上述的printf 语句出现在code更高版本。
And then the above printf statements occur later in the code.
因为从我个人理解， SIGSEGV 有关，形成不良的我包括的malloc 的东西是什么原因的malloc 来电。因此，如果数组的初始化是什么引起的问题，我想知道：
The reason I included the malloc stuff is because from what I understand, SIGSEGV is related to poorly formed malloc calls. So, if the array initializations are what's causing the problem, I would like to know:
- 为什么？
- 我怎么能修改
的malloccode来解决这个问题？
- why?
- how can I change the
malloccode to solve this problem?
我已经包括OS X所产生的崩溃日志，以防万一，可以帮助任何人出来。
I've included the crash log generated by OS X, just in case that helps anybody out.
Process: pole [5453]
Path: {REDACTED}
Identifier: pole
Version: ??? (???)
Code Type: X86-64 (Native)
Parent Process: bash [5441]
Date/Time: 2009-12-08 11:38:38.358 -0600
OS Version: Mac OS X 10.6.2 (10C540)
Report Version: 6
Interval Since Last Report: 130074 sec
Crashes Since Last Report: 68
Per-App Crashes Since Last Report: 63
Anonymous UUID: CA20CF15-8C46-4C85-A793-6C69F9F40140
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000100074f3b
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libSystem.B.dylib 0x00007fff828d489e __Balloc_D2A + 164
1 libSystem.B.dylib 0x00007fff828d49b8 __d2b_D2A + 45
2 libSystem.B.dylib 0x00007fff828e8c74 __dtoa + 320
3 libSystem.B.dylib 0x00007fff828aa960 __vfprintf + 4980
4 libSystem.B.dylib 0x00007fff828ec7db vfprintf_l + 111
5 libSystem.B.dylib 0x00007fff828ec75e fprintf + 196
6 pole 0x00000001000028b5 Balance::sarsa() + 187
7 pole 0x0000000100002e54 main + 49
8 pole 0x00000001000010a8 start + 52
Thread 0 crashed with X86 Thread State (64-bit):
rax: 0x0000000000000001 rbx: 0x000000010042cca0 rcx: 0x000000010042cca8 rdx: 0x0000000100074f3b
rdi: 0x000000000000000e rsi: 0x00007fff5fbfecbc rbp: 0x00007fff5fbfeba0 rsp: 0x00007fff5fbfeb90
r8: 0x00007fff5fbff0b0 r9: 0x0000000000000000 r10: 0x00000000ffffffff r11: 0x000000010083a40b
r12: 0x0000000000000001 r13: 0x00007fff5fbfecb8 r14: 0x00007fff5fbfecbc r15: 0x000000010000363e
rip: 0x00007fff828d489e rfl: 0x0000000000010202 cr2: 0x0000000100074f3b
Binary Images:
0x100000000 - 0x100003fff +pole ??? (???) {REDACTED}
0x7fff5fc00000 - 0x7fff5fc3bdef dyld 132.1 (???) /usr/lib/dyld
0x7fff81697000 - 0x7fff8169bff7 libmathCommon.A.dylib ??? (???) /usr/lib/system/libmathCommon.A.dylib
0x7fff8289c000 - 0x7fff82a5aff7 libSystem.B.dylib ??? (???) /usr/lib/libSystem.B.dylib
0x7fff83c4c000 - 0x7fff83cc9fef libstdc++.6.dylib ??? (???) /usr/lib/libstdc++.6.dylib
0x7fffffe00000 - 0x7fffffe01fff libSystem.B.dylib ??? (???) /usr/lib/libSystem.B.dylib
Model: MacBookPro4,1, BootROM MBP41.00C1.B03, 2 processors, Intel Core 2 Duo, 2.4 GHz, 2 GB, SMC 1.27f2
Graphics: NVIDIA GeForce 8600M GT, GeForce 8600M GT, PCIe, 256 MB
Memory Module: global_name
AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x8C), Broadcom BCM43xx 1.0 (5.10.91.19)
Bluetooth: Version 2.2.4f3, 2 service, 1 devices, 1 incoming serial ports
Network Service: AirPort, AirPort, en1
Serial ATA Device: Hitachi HTS542520K9SA00, 186.31 GB
Parallel ATA Device: MATSHITADVD-R UJ-867
USB Device: Built-in iSight, 0x05ac (Apple Inc.), 0x8502, 0xfd400000
USB Device: Apple Internal Keyboard / Trackpad, 0x05ac (Apple Inc.), 0x0230, 0x5d200000
USB Device: IR Receiver, 0x05ac (Apple Inc.), 0x8242, 0x5d100000
USB Device: BRCM2046 Hub, 0x0a5c (Broadcom Corp.), 0x4500, 0x1a100000
USB Device: Bluetooth USB Host Controller, 0x05ac (Apple Inc.), 0x820f, 0x1a110000感谢。
推荐答案
您在你的code没有相关的的printf 语句其它的错误。你踩在内存的某个地方，但问题并没有表现出来，直到的printf 尝试与 __ BAlloc_D2A ，它崩溃，因为它使用来跟踪空闲内存块堆的数据结构已被损坏。
You have a bug elsewhere in your code not related to the printf statement. You're stomping on memory somewhere, but the problem doesn't manifest itself until printf tries to allocate some memory with __BAlloc_D2A, which crashes because the heap data structures it uses to keep track of free memory blocks have been corrupted.
要尝试检测你在哪里上的内存跺脚，有许多可用的工具。如果你是在Linux上，我会建议使用的valgrind ，基本上运行在一个虚拟机中的code和告诉你只要你做任何事情一样的读/写内存越界非法读取未初始化的变量等。然而，这不是可在Mac OS X（还）。
To try to detect where you're stomping on memory, there are a number of tools available. If you were on Linux, I would suggest using valgrind, which essentially runs your code in a virtual machine and tells you whenever you do anything illegal like read/write memory out of bounds, read an uninitialized variable, etc. However, it's not available in Mac OS X (yet).
一种选择是使用<一href=\"http://developer.apple.com/Mac/library/documentation/Darwin/Reference/ManPages/man3/libgmalloc.3.html\"相对=nofollow> libgmalloc的：
% cat gmalloctest.c
#include <stdlib.h>
#include <stdio.h>
main()
{
unsigned *buffer = (unsigned *)malloc(sizeof(unsigned) * 100);
unsigned i;
for (i = 0; i < 200; i++) {
buffer[i] = i;
}
for (i = 0; i < 200; i++) {
printf ("%d ", buffer[i]);
}
}
% cc -g -o gmalloctest gmalloctest.c
% gdb gmalloctest
Reading symbols for shared libraries .. done
(gdb) set env DYLD_INSERT_LIBRARIES /usr/lib/libgmalloc.dylib
(gdb) r
Starting program: gmalloctest
Reading symbols for shared libraries .. done
GuardMalloc: Allocations will be placed on 16 byte boundaries.
GuardMalloc: - Some buffer overruns may not be noticed.
GuardMalloc: - Applications using vector instructions (e.g., SSE or Altivec) should work.
GuardMalloc: GuardMalloc version 19
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0xb000d000
0x00001f65 in main () at gmalloctest.c:10
10 buffer[i] = i;
(gdb) print i
$1 = 100
(gdb) where
#0 0x00001f65 in main () at gmalloctest.c:10
(gdb)
又见<一个href=\"http://developer.apple.com/mac/library/documentation/Performance/Conceptual/ManagingMemory/Articles/MallocDebug.html#//apple%5Fref/doc/uid/20001884-CJBJFIDD\"相对=nofollow>启用malloc调试功能。
这篇关于SIGSEGV，（貌似）引起的printf的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
