Unable do debug a .so library that makes my shell segfault [closed]

I am trying to make malloc, free and realloc functions in C (using mmap).

I am using following commands line to include them in my shell (I am using sh) :

export DYLD_LIBRARY_PATH=.
export DYLD_FORCE_FLAT_NAMESPACE=1
export DYLD_INSERT_LIBRARIES="./malloc.so:./free.so:./realloc.so"


Here is some of my malloc code :

#include "../incs/malloc.h"

void *malloc(size_t size)

write(2, "nMALLOC", 7);
t_block *res;

write(2, "0", 1);

res = NULL;

if (!(glob))

write(2, "1", 1);
// First call of malloc, need to init glob variable
glob = init_glob();

write(2, "2", 1);
res = get_block(size);
write(2, "3", 1);

if (!res)
return (NULL);

write(2, "4", 1);

return (res->memory);



I have a debug write too at the start of my init_glob() function.

When I execute the previous command lines in my shell, and run a random command (ls, for example), here is what I get :

MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01
MALLOC01Segmentation fault: 11


I don't really understand why it is not working, and how do debug this.

It should just write "MALLOC01" once, ten go to my init_glob function.
Why is this looping like this ?
How can i see WHERE it is crashing in ls command ?

Thanks in advance.

===== EDIT =====

Here is my init_glob() function :

#include "../incs/malloc.h"

/*
** This function returns a t_glob.
** It shall init the global variable of type t_glob, on the first time
** malloc is called in a process.
*/
t_glob *init_glob(void)

write(2, "a", 1);
t_glob *res;

res = NULL;

write(2, "b", 1);
res = (t_glob *)allocate_memory(sizeof(t_glob));

write(2, "c", 1);

res->tiny = NULL;
res->small = NULL;
res->large = NULL;
write(2, "d", 1);

return (res);



And my allocate_memory() function (but it seems that the program is not even going there) :

void *allocate_memory(size_t size)
MAP_PRIVATE, -1, 0);

return (res);



My t_glob struct is prototyped like this :

typedef struct s_glob

t_page *tiny;
t_page *small;
t_page *large;
// size_t sizeof_block; // Avoid repeat of sizeof() call
// size_t sizeof_page;
// size_t getpagesize_result;
t_glob;


This question appears to be off-topic. The users who voted to close gave this specific reason:

init_glob

1 Answer
1

I don't really understand why it is not working, and how do debug this.

The usual way to debug this is to let the program dump core (ulimit -c unlimited), and then look with the debugger where the infinite recursion happens.

core

ulimit -c unlimited

If I were to guess, I would guess that when the dynamic loader tries to resolve the call from malloc to init_glob, this dynamic symbol resolution itself needs dynamic memory and calls malloc.

malloc

init_glob

malloc

You would get a better answer (less guessing) if you provide MCVE, including build instructions.