Code debugging core step memory

Location method ：

1. gdb:
   1. adopt gdb For memory break points （watch） , See who illegally accessed the memory area . Then gradually narrow the scope . Until the corresponding function segment is found , such as ：
      1. For example, discovery 0x800 The address is trampled .
         1. First, judge whether the address is legal , That is to say 0x800 Whether it should exist , If it should not exist , Then you can watch This address , You can also keep the code running , During this period, the address is continuously printed , See which code has been modified .
   2. limited
      1. The problem occurs in the startup phase , There is no time to set a breakpoint , Bad positioning ,
      2. Some systems do not support gdb
      3. Trampled address is not fixed
2.   Problems like memory leaks , Predetermination , Post positioning , Through memory proc Information （meminfo/media-mem） Judgment is a specific module , Memory segment . It can also be used. MMU(linux You can use mrotect) Protect specific areas
   1. limited
      1. MMU The smallest unit of protection is a memory page , The area that may be trampled is small , No use mmu To protect
3.   Subtraction reduces the range , Clipping module , Modify the application , Find the smallest scene
4. Add print , Print out the abnormal and suspicious address ; It's fine too dump Output the data of the trampled address , View data characteristics , Analyze where it comes from according to data characteristics .
5. valgrind+effence+ksan Tools such as

Common questions

1. Type conversion error
   1. For example, small to large , Including common char and int, And custom structures
   2. Including formal parameters
2. Use the address that has been released
   1. such as malloc Or use without applying for control
3. The requested memory is too small , Not enough use , Similar and cross-border

How to avoid

1. Function nesting should not be too deep
2. Code should be symmetrical ,malloc The corresponding position must be released
3. Pay attention to the size of the array