如何让android的bionic中的linker输出调试信息

缺省情况下bionic的linker是不会输出调试信息的，因为Linker.c里一开始就写着：

 * Do NOT use malloc() and friends or pthread_*() code here.
 * Don't use printf() either; it's caused mysterious memory
 * corruption in the past.
 * The linker runs before we bring up libc and it's easiest
 * to make sure it does not depend on any complex libc features

而他的调试信息基本都是printf到stdout的。

所以要改下面几个地方：

1、linker_debug.h中的#define LINKER_DEBUG和#define TRACE_DEBUG都改为1。

 

2、linker.c中的

#define HOODLUM(name, ret, ...)                                               \
    ret name __VA_ARGS__                                                      \
    {                                                                         \
        char errstr[] = "ERROR: " #name " called from the dynamic linker!\n"; \
        write(2, errstr, sizeof(errstr));                                     \
        abort();                                                              \
    }
HOODLUM(malloc, void *, (size_t size));
HOODLUM(free, void, (void *ptr));
HOODLUM(realloc, void *, (void *ptr, size_t size));
HOODLUM(calloc, void *, (size_t cnt, size_t size));

这一段注释掉。

 

3、Android.mk中的LOCAL_STATIC_LIBRARIES := libcutils libc_nomalloc改成

LOCAL_STATIC_LIBRARIES := libcutils libc。

原因是bionic的libc的android.mk中的一段话：

# ========================================================
# libc_nomalloc.a
# ========================================================
#
# This is a version of the static C library that does not
# include malloc. It's useful in situations when calling
# the user wants to provide their own malloc implementation,
# or wants to explicitly disallow the use of the use of malloc,
# like the dynamic loader.

 

所以缺省的linker自己实现了malloc,free,realloc,calloc几个函数（2中说的），调用这几个函数

就输出错误信息然后退出了。

 

4、重新编译linker，上传到模拟器或实际设备，export DEBUG=3,然后执行命令就看到linker输出的log了。