How to trace "tcmalloc : large alloc .... "

Question

my app print several line like:

tcmalloc: large alloc 4294488064 bytes == 0x2b968d8000 @  0x727432 0x727302 0x727a58    0x75a07d 0x574beb 0x585756 0x5575df 0x5717db 0x57108f 0x58078c 0x302b80610a
tcmalloc: large alloc 4294488064 bytes == 0x2c97063000 @  0x727432 0x727302 0x727a58   0x75a07d 0x574beb 0x585756 0x5575df 0x5717db 0x57108f 0x58078c 0x302b80610a
tcmalloc: large alloc 4294488064 bytes == 0x2b968d8000 @  0x727432 0x727302 0x727a58 0x75a07d 0x574beb 0x585756 0x5575df 0x5717db 0x57108f 0x58078c 0x302b80610a

where does this message comes from? does it means my app has some bugs or memory-leak? how can I trace the root cause?

Hospitalet

to trace the mem address to a line in your code, use addr2line commandline tool.. use it as addr2line -e <executable name> then press enter and then paste an address and press enter. – Diuretic

Thanks. in this case, I paste the address at the end of lines, but get a "??:0" – Hospitalet

you have to compile it using -g option. – Diuretic

Answer 1

See http://code.google.com/p/gperftools/source/browse/trunk/src/tcmalloc.cc?r=80&redir=1 line 843

Depending on your application - the large allocation may or may not be a bug.

In any case - the part after the @ mark is a stack trace and can be used to locate the source of the message

The repeating number (4294488064 which seems to be equal to 4G-479232 or 0x100000000-0x75000) makes me suspect the original allocation call got a negative signed value and used it as an unsigned value.

Saccharase

thanks, that is very helpful. the bug is just like you said, caused by mixing use of unsigned and signed value – Hospitalet

Answer 2

If you still have the process running or were able to core dump it (kill -ABRT) then you should be able to attach gdb and run the info symbol <address> command (<address> is one of those hexadecimal numbers after @ in the error message: 0x727432 ...).

In my case it was an authentic error.

Revocation