Strange behaviour of compiler (Same code is not working now)
Posted: Sat Dec 24, 2016 11:47 am
Hello forum.
I had a really really strange something today. I wrote my keyboard-read-key code about 2 weeks ago and today I used it again. It was working, but it is not working now.
The only modification was I did recompiling gcc with --with-newlib because I forgot it before. I returned back to old compiler, but problem is still persist.
It should work, but it is not working now.
I know it is bad, but I'm going to make it better later.
Surprisingly, it works if I make it:
That made me suspect about optimization for recursive functions, but with -O0 problem still persist, too 
That problem is really strange for me. Also I have another now-not-working code, too.
Newlib was handling backspace itself great, but now it is not handling it, too.
That code was working, but it is not working now, like the other code.
In that code if I send an output to newlib like xyz\b\b\babcdef;
It results with str[0] is x, str[1] is y, str[2] is z, str[3] is \b, str[4] is \b, str[5] is \b, str[6] is a, str[7] is b, str[8] is c, ...
printf prints the correct text, abcdef (surprisingly), but strncmp or strcmp says strings are not same. I'm sure it was working before.
That is my read syscall:
Is it a really unnoticed gcc bug or I didn't notice that until today (but I don't believe that, I'm sure it was working)
Help please
GCC version 6.2.0, Binutils version 2.27, Newlib version 2.2.0-1
Why it is happening?
I had a really really strange something today. I wrote my keyboard-read-key code about 2 weeks ago and today I used it again. It was working, but it is not working now.
The only modification was I did recompiling gcc with --with-newlib because I forgot it before. I returned back to old compiler, but problem is still persist.
It should work, but it is not working now.
Code: Select all
char keyboard_getchar()
{
while (!(inb(0x64) & 0x1));
unsigned char scancode = inb(0x60);
if (scancode & 0x80) keyboard_getchar();
char chr = key_list[scancode];
terminal_putchar(chr);
return chr;
}Surprisingly, it works if I make it:
Code: Select all
char keyboard_getchar()
{
X:
while (!(inb(0x64) & 0x1));
unsigned char scancode = inb(0x60);
if (scancode & 0x80) goto X;
char chr = key_list[scancode];
terminal_putchar(chr);
return chr;
}That problem is really strange for me. Also I have another now-not-working code, too.
Newlib was handling backspace itself great, but now it is not handling it, too.
Code: Select all
void rw_test()
{
char *str = malloc(50);
printf("Enter some string: ");
gets(str);
printf("The string you entered: %s\n", str);
if (!strncmp("abcdef", str, 6))
{
printf("You entered abcdef, yay!");
}
}In that code if I send an output to newlib like xyz\b\b\babcdef;
It results with str[0] is x, str[1] is y, str[2] is z, str[3] is \b, str[4] is \b, str[5] is \b, str[6] is a, str[7] is b, str[8] is c, ...
printf prints the correct text, abcdef (surprisingly), but strncmp or strcmp says strings are not same. I'm sure it was working before.
That is my read syscall:
Code: Select all
int read(int file, char *ptr, int len) {
if (file == 1) {
*ptr = keyboard_getchar();
return 1;
}
else
{
return -1; //Until fixing that problem I won't add VFS read code
}
}Help please
GCC version 6.2.0, Binutils version 2.27, Newlib version 2.2.0-1
Why it is happening?