CS 330 Lecture 16 – Assembly
February 26, 2012 by Chris Johnson. Filed under
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cs330, lectures, spring 2012.
Agenda
- a little peek at GNU Assembly
- code transformation
- to preprocessed
- to assembly
- to object code
- to linked executable
- variables? no, registers
- %ebp and %esp
- on call and return
- local variables
- %eax for return values
- passing arguments to functions
- arrays
- pointers
- conditional statements
- loops
Code
ls.c
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <sys/types.h>
int main(int argc, char **argv) {
for (int i = 0; i < argc; ++i) {
printf("argv[%d]: %s\n", i, argv[i]);
}
char path[256];
printf("Directory?\n");
int result = scanf("%s", path);
if (result == EOF) {
printf("...... Okay.\n");
exit(1);
}
DIR *dir = opendir(path);
struct dirent *entry;
while (entry = readdir(dir)) {
printf("entry->d_name: %s\n", entry->d_name);
}
closedir(dir);
/* free(dir); */
/* free(entry); */
return 0;
}
assembly.mk
%.s: %.c
gcc -fno-asynchronous-unwind-tables -Wall -std=c99 -S -o $@ $<
clean:
rm -f *.s
noop.c
void foo() {
5 + 7;
}
twofuncs.c
void a(int i) {
}
void b() {
a(5);
}
if.c
int max(int a, int b) {
if (a > b) {
return a;
} else {
return b;
}
}
loop.c
void print() {
for (int i = 0; i < 5; ++i) {
}
}
Haiku
Machine code, Latin.
Both unknown. But machine code…
All roads lead to it.