I’m working on a compiler in c (flex/bison) and I have this segfault that I just can’t figure out, I’ve tried gdb and know where it is caused but everything I’ve tried doesn’t seem to resolve it.

4+3; 
lex: création token NUMBER 4
lex: création token +
lex: création token NUMBER 3
lex: création token ;
lex: fin de lecture

Parsing:: c'est bien une expression
ast de l'expression:
[ :: [ [ :4.00: ] :+: [ :3.00: ] ] ] 

Program received signal SIGSEGV, Segmentation fault.
0x0000555555558315 in print_prog (p=0x4008000000000000) at AST.c:158
158         if(NULL != p->command){ 
(gdb) backtrace 
#0  0x0000555555558315 in print_prog (p=0x4008000000000000) at AST.c:158
#1  0x0000555555558348 in print_prog (p=0x555555561c00) at AST.c:161
#2  0x00005555555552c1 in main () at main.c:19

I’ll provide some of my file for context
so these are parts of my ast.h and ast.c files
ast.h

struct _expr_tree {
  char rule;                    /* "name" of the rule/operation operation */
  float number;                   /* int  for value */
  struct _expr_tree* left;           /* NULL if unary node or leaf*/
  struct _expr_tree* right;          /* used for unary node but NULL if leaf */
  bool BOOLEAN;
  char *VAR;
};

typedef struct _expr_tree* AST_expr;

struct _command_tree {
  char rule;                    /* "name" of the rule/operation operation */
  int taille;
  AST_expr expr1;
  struct _command_tree* then_comm;
  struct _command_tree* else_comm;              /* used for command with at least one sub-expression */
};

typedef struct _command_tree* AST_comm;

struct _program_tree {
    char rule;
    int taille;
    AST_comm command;        
    struct _program_tree* next;
};
typedef struct _program_tree* AST_prog;

ast.c

AST_comm new_command(AST_expr expression){
  AST_comm t =  malloc(sizeof(struct _command_tree));
  if (t!=NULL){ /* malloc ok */
    t->expr1 = expression;
  } else printf("ERR : MALLOC ");
  return t;

}

AST_prog new_prog(AST_comm c, AST_prog next){
    AST_prog p = malloc(sizeof(struct _program_tree));
    if(p!=NULL){
        p->command = c;
        p->next = next;
        p->rule = '';
        p->taille = 0;
    } else printf("ERR : malloc");
    return p;
}

parser

programme: 
    | commande programme 
      { *rez = new_prog($1, $2); }
    ; 

commande: expression ';'
    { $$ = new_command($1); }
    | I '(' expression ')' commande ';' S commande ';'
           { $$ = new_if_else_expr($3, $5, $8); }
        ; 

I tried casting the AST_prog in new_prog function but it didn’t work, I also wrote NULL first in every if statement but it still didn’t solve much. I’m this point I’m kinda lost.
Any help is welcomed and thank you all for reading !