“分段错误（核心转储）”：libioP.h、printf-parse.h、vfprintf-internal.c 等的“没有此类文件或目录”

核心转储文件中的示例错误：

1289    vfprintf-internal.c: No such file or directory.

111 printf-parse.h: No such file or directory.

948 libioP.h: No such file or directory.

948 libioP.h: No such file or directory.

我正在研究 fast_malloc() 实现，但一旦我覆盖，就会因未知原因而出现分段错误malloc() and free()用我自己的实现，但不是在那之前（意思是，如果我打电话fast_malloc()没关系，但如果我想打电话malloc()为了得到我的实现，它似乎被破坏了）。

为什么会出现段错误？

在打印任何内容之前的示例输出，包括开头的打印语句main()，以及我里面的一些调试打印fast_malloc():

Segmentation fault (core dumped)

我已打开核心转储正如我在这里解释的.

So, gdb path/to/my/executable core显示以下一些内容core文件信息。请注意，每次运行可能会针对“没有此类文件或目录”中缺少的文件产生不同的语句。

1. One run:

Reading symbols from build/fast_malloc_unit_tests...

warning: core file may not match specified executable file.
[New LWP 1257155]
Core was generated by `build/fast_malloc_unit_tests'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007fd50fc7ba01 in __vfprintf_internal (s=0x7fd50fdee6a0 <_IO_2_1_stdout_>, 
    format=0x5622fd1b8010 "DEBUG: %s():\n", ap=ap@entry=0x7ffec28300a0, 
    mode_flags=mode_flags@entry=0) at vfprintf-internal.c:1289
1289    vfprintf-internal.c: No such file or directory.
(gdb) bt
#0  0x00007fd50fc7ba01 in __vfprintf_internal (s=0x7fd50fdee6a0 <_IO_2_1_stdout_>, 
    format=0x5622fd1b8010 "DEBUG: %s():\n", ap=ap@entry=0x7ffec28300a0, 
    mode_flags=mode_flags@entry=0) at vfprintf-internal.c:1289
#1  0x00007fd50fc66ebf in __printf (format=<optimized out>) at printf.c:33
#2  0x00005622fd1b53eb in fast_malloc (num_bytes=1024) at src/fast_malloc.c:225
#3  0x00005622fd1b5b66 in malloc (num_bytes=1024) at src/fast_malloc.c:496
#4  0x00007fd50fc86e84 in __GI__IO_file_doallocate (fp=0x7fd50fdee6a0 <_IO_2_1_stdout_>)
    at filedoalloc.c:101
#5  0x00007fd50fc97050 in __GI__IO_doallocbuf (fp=fp@entry=0x7fd50fdee6a0 <_IO_2_1_stdout_>)
    at libioP.h:948
#6  0x00007fd50fc960b0 in _IO_new_file_overflow (f=0x7fd50fdee6a0 <_IO_2_1_stdout_>, ch=-1)
    at fileops.c:745
#7  0x00007fd50fc94835 in _IO_new_file_xsputn (n=7, data=<optimized out>, f=<optimized out>)
    at libioP.h:948
#8  _IO_new_file_xsputn (f=0x7fd50fdee6a0 <_IO_2_1_stdout_>, data=<optimized out>, n=7)
    at fileops.c:1197
#9  0x00007fd50fc7baf2 in __vfprintf_internal (s=0x7fd50fdee6a0 <_IO_2_1_stdout_>, 
    format=0x5622fd1b8010 "DEBUG: %s():\n", ap=ap@entry=0x7ffec28308e0, 
    mode_flags=mode_flags@entry=0) at ../libio/libioP.h:948
#10 0x00007fd50fc66ebf in __printf (format=<optimized out>) at printf.c:33
#11 0x00005622fd1b53eb in fast_malloc (num_bytes=1024) at src/fast_malloc.c:225
#12 0x00005622fd1b5b66 in malloc (num_bytes=1024) at src/fast_malloc.c:496
--Type <RET> for more, q to quit, c to continue without paging--q
Quit
(gdb) q

2. 另一个：

Reading symbols from build/fast_malloc_unit_tests...

warning: core file may not match specified executable file.
[New LWP 1257787]
Core was generated by `build/fast_malloc_unit_tests'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f20b0bbba80 in __find_specmb (
    format=0x5644c516d108 "DEBUG:   block_map_i = %zu (num_bytes requested to allocate = %zu; smallest user block size large enough = %zu)\n") at printf-parse.h:111
111 printf-parse.h: No such file or directory.
(gdb) bt
#0  0x00007f20b0bbba80 in __find_specmb (
    format=0x5644c516d108 "DEBUG:   block_map_i = %zu (num_bytes requested to allocate = %zu; smallest user block size large enough = %zu)\n") at printf-parse.h:111
#1  __vfprintf_internal (s=0x7f20b0d2e6a0 <_IO_2_1_stdout_>, 
    format=0x5644c516d108 "DEBUG:   block_map_i = %zu (num_bytes requested to allocate = %zu; smallest user block size large enough = %zu)\n", ap=ap@entry=0x7ffe7f6ea580, mode_flags=mode_flags@entry=0)
    at vfprintf-internal.c:1365
#2  0x00007f20b0ba6ebf in __printf (format=<optimized out>) at printf.c:33
#3  0x00005644c516a47d in fast_malloc (num_bytes=1024) at src/fast_malloc.c:244
#4  0x00005644c516ab4e in malloc (num_bytes=1024) at src/fast_malloc.c:496
#5  0x00007f20b0bc6e84 in __GI__IO_file_doallocate (fp=0x7f20b0d2e6a0 <_IO_2_1_stdout_>)
    at filedoalloc.c:101
#6  0x00007f20b0bd7050 in __GI__IO_doallocbuf (fp=fp@entry=0x7f20b0d2e6a0 <_IO_2_1_stdout_>)
    at libioP.h:948
#7  0x00007f20b0bd60b0 in _IO_new_file_overflow (f=0x7f20b0d2e6a0 <_IO_2_1_stdout_>, ch=-1)
    at fileops.c:745
#8  0x00007f20b0bd4835 in _IO_new_file_xsputn (n=23, data=<optimized out>, f=<optimized out>)
    at libioP.h:948
#9  _IO_new_file_xsputn (f=0x7f20b0d2e6a0 <_IO_2_1_stdout_>, data=<optimized out>, n=23)
    at fileops.c:1197
#10 0x00007f20b0bbbaf2 in __vfprintf_internal (s=0x7f20b0d2e6a0 <_IO_2_1_stdout_>, 
    format=0x5644c516d108 "DEBUG:   block_map_i = %zu (num_bytes requested to allocate = %zu; smallest--Type <RET> for more, q to quit, c to continue without paging--q
Quit
(gdb) q

3. another:

Reading symbols from build/fast_malloc_unit_tests...

warning: core file may not match specified executable file.
[New LWP 1258037]
Core was generated by `build/fast_malloc_unit_tests'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f901ef65e4d in __GI__IO_file_doallocate (fp=0x7f901f0cd6a0 <_IO_2_1_stdout_>)
    at libioP.h:948
948 libioP.h: No such file or directory.
(gdb) q

4. another

Reading symbols from build/fast_malloc_unit_tests...

warning: core file may not match specified executable file.
[New LWP 1258336]
Core was generated by `build/fast_malloc_unit_tests'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f5e4b551a80 in __find_specmb (
    format=0x562fac6d7108 "DEBUG:   block_map_i = %zu (num_bytes requested to allocate = %zu; smallest user block size large enough = %zu)\n") at printf-parse.h:111
111 printf-parse.h: No such file or directory.
(gdb) q

My gcc目前的构建选项：

-Wall -Wextra -Werror -O0 -ggdb -std=c11 -save-temps=obj -DDEBUG

可能与此有关DEBUG_PRINTF()我有宏，我在里面调用它fast_malloc().

#ifdef DEBUG
    /// Debug printf function.
    /// See: https://stackoverflow.com/a/1941336/4561887
    #define DEBUG_PRINTF(...) printf("DEBUG: "__VA_ARGS__)
#else
    #define DEBUG_PRINTF(...) \
        do                    \
        {                     \
        } while (0)
#endif

Why is malloc()无论如何，在程序开始之前就被调用？我不叫它anywhere。但是，请注意你可以看到malloc()在运行 1 和 2 的堆栈跟踪中可以看到，调用了 1024 字节（虽然每次运行都会发生这种情况，但这些是我粘贴的足够多的内容，您可以在其中看到它）。

My malloc() and free()覆盖看起来像这样：

inline void* malloc(size_t num_bytes)
{
    return fast_malloc(num_bytes);
}

inline void free(void* ptr)
{
    fast_free(ptr);
}

我的单线程程序在哪里malloc()是否神秘地被调用而没有我在启动时以某种方式调用它多线程？是否发生了一些奇怪的程序初始化事情？我的fast_malloc()实现目前不是线程安全的，因此如果 Linux 在某种程序初始化或其他过程中执行一些奇怪的多线程 malloc() 调用，这可能是损坏的原因，同样，fast_malloc()，这会覆盖malloc()，还不是线程安全的。

这似乎与里面印刷malloc()。里面正在打印malloc()禁止？

这是来自核心转储的最近堆栈跟踪的底部（第一次调用位于最底部）：

#127471 0x00005626d43dca28 in malloc (num_bytes=1024) at src/fast_malloc.c:494
#127472 0x00007faa222a7e84 in __GI__IO_file_doallocate (fp=0x7faa2240f6a0 <_IO_2_1_stdout_>) at filedoalloc.c:101
#127473 0x00007faa222b8050 in __GI__IO_doallocbuf (fp=fp@entry=0x7faa2240f6a0 <_IO_2_1_stdout_>) at libioP.h:948
#127474 0x00007faa222b70b0 in _IO_new_file_overflow (f=0x7faa2240f6a0 <_IO_2_1_stdout_>, ch=-1) at fileops.c:745
#127475 0x00007faa222b5835 in _IO_new_file_xsputn (n=13, data=<optimized out>, f=<optimized out>) at libioP.h:948
#127476 _IO_new_file_xsputn (f=0x7faa2240f6a0 <_IO_2_1_stdout_>, data=<optimized out>, n=13) at fileops.c:1197
#127477 0x00007faa222aa678 in __GI__IO_puts (str=0x5626d43df227 '=' <repeats 13 times>) at libioP.h:948
#127478 0x00005626d43dca28 in malloc (num_bytes=1024) at src/fast_malloc.c:494
#127479 0x00007faa222a7e84 in __GI__IO_file_doallocate (fp=0x7faa2240f6a0 <_IO_2_1_stdout_>) at filedoalloc.c:101
#127480 0x00007faa222b8050 in __GI__IO_doallocbuf (fp=fp@entry=0x7faa2240f6a0 <_IO_2_1_stdout_>) at libioP.h:948
#127481 0x00007faa222b70b0 in _IO_new_file_overflow (f=0x7faa2240f6a0 <_IO_2_1_stdout_>, ch=-1) at fileops.c:745
#127482 0x00007faa222b5835 in _IO_new_file_xsputn (n=13, data=<optimized out>, f=<optimized out>) at libioP.h:948
#127483 _IO_new_file_xsputn (f=0x7faa2240f6a0 <_IO_2_1_stdout_>, data=<optimized out>, n=13) at fileops.c:1197
#127484 0x00007faa222aa678 in __GI__IO_puts (str=0x5626d43df227 '=' <repeats 13 times>) at libioP.h:948
#127485 0x00005626d43dca28 in malloc (num_bytes=1024) at src/fast_malloc.c:494
#127486 0x00007faa222a7e84 in __GI__IO_file_doallocate (fp=0x7faa2240f6a0 <_IO_2_1_stdout_>) at filedoalloc.c:101
#127487 0x00007faa222b8050 in __GI__IO_doallocbuf (fp=fp@entry=0x7faa2240f6a0 <_IO_2_1_stdout_>) at libioP.h:948
#127488 0x00007faa222b70b0 in _IO_new_file_overflow (f=0x7faa2240f6a0 <_IO_2_1_stdout_>, ch=-1) at fileops.c:745
#127489 0x00007faa222b5835 in _IO_new_file_xsputn (n=49, data=<optimized out>, f=<optimized out>) at libioP.h:948
#127490 _IO_new_file_xsputn (f=0x7faa2240f6a0 <_IO_2_1_stdout_>, data=<optimized out>, n=49) at fileops.c:1197
#127491 0x00007faa222aa678 in __GI__IO_puts (str=0x5626d43df238 "Running UNIT tests for the \"fast_malloc\" module.\n") at libioP.h:948
#127492 0x00005626d43dca98 in main () at src/fast_malloc_unit_tests.c:35
(gdb) 

什么是__GI__IO_puts and _IO_new_file_xsputn当你向上移动时，还有那些其他函数调用？他们在其他线程中调用吗？他们在打电话吗malloc()幕后？它出现__GI__IO_file_doallocate is...

你正在呼唤printf在你的malloc执行。这不会有好结果。

在堆栈跟踪中，您可以清楚地看到printf itself calls malloc.

If your malloc不准备在操作其数据结构时被调用，它会崩溃（可能就是这里发生的情况）。

或者，您也可以以无限递归结束，当malloc calls printf，这称为malloc，这称为printf, etc.

TL;DR：当实现低级别的东西时malloc, you must坚持使用本身不分配任何东西的低级函数，或者直接系统调用。

为什么 malloc() 在程序启动之前被调用？

因为低级函数例如动态加载器在自身初始化时需要分配内存。

你的mallocmust在流程生命周期的早期工作；很久之前main.

malloc() 内的打印是否被禁止？

一切禁止可能分配内存的行为。

在实践中，您只需要调用异步信号安全例程，因为非异步信号安全例程may分配，如果不是现在，那么将来也会分配。