Linux - finding the executable path reliably (no /proc, invalid argv[0] from caller)

fakeme.c

// run supplied program but with argv[0] replaced by 'FAKEME'

#include <unistd.h>

int main(int argc, char **argv) {
  char *file = argv[1];
  argv[1] = "FAKEME!";
  execvp(file, &argv[1]);
}

findme.c

// experiments in locating one's own executable path
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/auxv.h>

int main(int argc, char **argv) {
	// grab the AUXV_EXECFN path
	char *cwd = getcwd(NULL, 0);
	char *path = (char *)getauxval(AT_EXECFN);
	if (!cwd) {
		puts("getcwd() returns NULL?");
		return 1;
	}
	if (!path) {
		puts("AT_EXECFN not available?");
		return 2;
	}
	char *me = path;
	// resolve non-absolute path's via cwd
	if (path[0]!='/') {
		char *srch = malloc(strlen(cwd)+strlen(path)+2);
		strcpy(srch, cwd);
		strcat(srch, "/");
		strcat(srch, path);
		me = realpath(srch, NULL);
	}
	printf("cwd=%s, argv[0]=%s, AT_EXECFN=%s me=%s\n", cwd, argv[0], path, me);
	return 0;
}

Makefile

# Build/test findme program

all: tests

clean:
	@rm -rf fakeme findme

tests: bins
	@echo '--- Run directly from the shell, relative location ---'
	./findme
	@echo '--- Run directly from the shell, absolute location ---'
	$$PWD/findme
	@echo '--- Run with a fake argv[0], relative location ---'
	./fakeme ./findme
	@echo '--- Run with a fake argv[0], absolute location ---'
	./fakeme $$PWD/findme
	@echo '--- Run via the PATH, no location ---'
	PATH=$$PATH:$$PWD findme
	@echo '--- Run via the PATH, fake argv[0] ---'
	PATH=$$PATH:$$PWD fakeme findme

bins: fakeme findme

%: %.c
	gcc -o $@ $<