I am having a slight problem with some structs in a kernel module I'm building, so I thought it would be nice if there was an easy way to print out structs and their values - and below is a small userland example of what I mean.
Say we have the simple C example as below (given in form of a bash commands):
FN=mtest
cat > $FN.c <<EOF
#include <stdio.h> //printf
#include <stdlib.h> //calloc
struct person
{
int age;
int height;
};
static struct person *johndoe;
main ()
{
johndoe = (struct person *)calloc(1, sizeof(struct person));
johndoe->age = 6;
asm("int3"); //breakpoint for gdb
printf("Hello World - age: %d\n", johndoe->age);
free(johndoe);
}
EOF
gcc -g -O0 $FN.c -o $FN
# just a run command for gdb
cat > ./gdbcmds <<EOF
run
EOF
gdb --command=./gdbcmds ./$FN
If we run this example, the program will compile, and gdb will run it, and automatically stop at the breakpoint. Here we can do the following:
Program received signal SIGTRAP, Trace/breakpoint trap.
main () at mtest.c:20
20 printf("Hello World - age: %d\n", johndoe->age);
(gdb) p johndoe
$1 = (struct person *) 0x804b008
(gdb) p (struct person)*0x804b008
$2 = {age = 6, height = 0}
(gdb) c
Continuing.
Hello World - age: 6
Program exited with code 0300.
(gdb) q
As shown, in gdb we can printout (dump?) the value of the struct pointer johndoe as {age = 6, height = 0} ... I would like to do the same, but directly from a C program; say as in the following example:
#include <stdio.h> //printf
#include <stdlib.h> //calloc
#include <whatever.h> //for imaginary printout_struct
struct person
{
int age;
int height;
};
static struct person *johndoe;
static char report[255];
main ()
{
johndoe = (struct person *)calloc(1, sizeof(struct person));
johndoe->age = 6;
printout_struct(johndoe, report); //imaginary command
printf("Hello World - age: %d\nreport: %s", johndoe->age, report);
free(johndoe);
}
which would result with an output like:
Hello World - age: 6
$2 = {age = 6, height = 0}
So my question is - does a function like that imaginary printout_struct exist - or is there another approach to make a printout like this possible?
Thanks in advance for any help,
Cheers!