execvep vs. proc/environ

gistfile1.txt

#define _GNU_SOURCE
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/wait.h>

int main(int argc, char* argv[], char* envp[]) {
    pid_t ppid = getppid();
    pid_t go = 0;
    char* envv = NULL;
    int status;

    if(argc > 1) {
        go = atoi(argv[1]);
        printf("[0] Explicit parent: %u\n",  go);
    }

    envv = getenv("LD_PRELOAD_ME");
    printf("[1] Just started: me=%u, ppid=%u\n", getpid(), getppid());
    printf("[2] Env: LD_PRELOAD_ME=%s\n", envv ? envv : "<not-set>");

    if (ppid != go) { 
        printf("[3.C] After fork()/exec(). Check my /proc/%u/environ. sleeping...\n", getpid());
        sleep(30);
        exit(0);
    }

    pid_t pid = fork();
    if (pid == -1) {
        printf("Can't actually fork.Punt!\n");
        exit(1);
    } else if (pid == 0) {
        printf("[3.C] In forked child: me=%u, ppid=%u\n", getpid(), getppid());
        envv = getenv("LD_PRELOAD_ME");
        printf("[3.C] Env(pre-exec): LD_PRELOAD_ME=%s\n", envv ? envv : "<not-set>" );
        argv[1] = NULL;
        if (execvpe(argv[0], argv, NULL) == -1) {
            printf("Failed to exec.Burp!");
            exit(1);
        }
    } else {
        printf("[3.P] In fork parent: me=%u, child=%u, ppid=%u\n", getpid(), pid, getppid());
        if(waitpid(pid, &status, 0) > 0 ) {
            printf("[4] ok, child exited\n");
        } else {
            printf("waitpid() failed\n");
            exit(1);
        }
        exit(0);
    }
    return 0;
}

# export LD_PRELOAD_ME=something-nice
# ./ex $$
[0] Explicit parent: 1505
[1] Just started: me=3527, ppid=1505
[2] Env: LD_PRELOAD_ME=something-nice
[3.P] In fork parent: me=3527, child=3528, ppid=1505
[3.C] In forked child: me=3528, ppid=3527
[3.C] Env(pre-exec): LD_PRELOAD_ME=something-nice
[1] Just started: me=3528, ppid=3527
[2] Env: LD_PRELOAD_ME=<not-set>
[3.C] After fork()/exec(). Check my /proc/3528/environ. sleeping...
[4] ok, child exited