Miscellaneous Debugging tips

LTRACE
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from the Man page
ltrace  is  a  program  that  simply  runs the specified command until it exits.  It intercepts and records the  dynamic library calls which are called by the executed process and the  signals  which  are  received  by  that        process.  It can also intercept and print the system calls executed by the program.





STRACE
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In the simplest case strace runs the specified command until it exits.  It intercepts and  records  the  system  calls  which  are called by a process and the signals which are received by a process.  The name of each system  call, its arguments and its return value are printed on standard error or to the file  specified  with  the  -o    option.



nemesis@nemesis-laptop:~/test_code$ strace ./crashcourse
execve("./crashcourse", ["./crashcourse"], [/* 42 vars */]) = 0
brk(0)                                  = 0x80ba000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7846000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=72786, ...}) = 0
mmap2(NULL, 72786, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7834000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/tls/i686/cmov/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\260l\1\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1319364, ...}) = 0
mmap2(NULL, 1325416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x626000
mmap2(0x764000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x13e) = 0x764000
mmap2(0x767000, 10600, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x767000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7833000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb78336c0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0x764000, 8192, PROT_READ)     = 0
mprotect(0x8049000, 4096, PROT_READ)    = 0
mprotect(0x3d0000, 4096, PROT_READ)     = 0
munmap(0xb7834000, 72786)               = 0
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++


MTRACE
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nemesis@nemesis-laptop:~/test_code$ mtrace ./crashcourse
No memory leaks