Several bugs of Null Pointer Dereference/Unchecked Return Value to NULL Pointer Dereference

[yuxuan He]

Ubuntu version: 18.04
bcc version:0.16.17

I found several bugs in bcc , would you help me to check if these bugs are true?thanks for your patience.
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step 1 :
  In file build/ar/ar.c(build is directory generated by configure) , function prev_mapelt line 775 :
    Select the false branch at this point (tail->next!=null is false)

step 2 :
  In file build/ar/ar.c(build is directory generated by configure) , function prev_mapelt line 777 :
    Return null to caller

step 3 :
  In file build/ar/ar.c(build is directory generated by configure) , function move_in_map line 1332 :
    Function prev_mapelt executes and stores the return value to prev (prev can be null)

step 4 :
  In file build/ar/ar.c(build is directory generated by configure) , function move_in_map line 1333 :
    Store this->next to prev->next
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step 1 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function insert_substrings line 1403 :
    Allocate memory to rv (lacking failure check, 7 out of 19 memory allocations checked failures)

step 2 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function insert_substrings line 1403 :
    Store 0 to rv

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step 1 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function insert_substrings line 1403 :
    Allocate memory to rv (lacking failure check, 7 out of 19 memory allocations checked failures)

step 2 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function insert_substrings line 1457 :
    Select the false branch at this point ((cc.0.ph.lcssa25+2)>len.0.ph.ph is false)

step 3 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function insert_substrings line 1458 :
    Store *(data_str) to rv[cc]

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step 1 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function gen_substrings line 1271 :
    Allocate memory to arg_list (lacking failure check, 7 out of 19 memory allocations checked failures)

step 2 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function gen_substrings line 1272 :
    arg_list is used as the 1st parameter in function memset (arg_list can be null)

===============================================================================================

step 1 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function gen_substrings line 1271 :
    Allocate memory to arg_list (lacking failure check, 7 out of 19 memory allocations checked failures)

step 2 :
  In file build/cpp/cpp.c(build is directory generated by configure) , function gen_substrings line 1277 :
    Load value from arg_list[ac.0].name

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