libc: preserve short program invocation names

host/test/exec.test.ts

@@ -23,16 +23,21 @@ describe("execve", () => {
       argv: ["exec-caller"],
       timeout: 15_000,
       execPrograms,
+      useDefaultRootfs: false,
     });
 
     // exec-child exits with 42
     expect(result.exitCode).toBe(42);
 
     // exec-child prints its argv
     expect(result.stdout).toContain("argc=3");
-    expect(result.stdout).toContain("argv[0]=exec-child");
+    expect(result.stdout).toContain("argv[0]=/opt/kandelo/bin/exec-child");
     expect(result.stdout).toContain("argv[1]=hello");
     expect(result.stdout).toContain("argv[2]=world");
+    expect(result.stdout).toContain(
+      "program_invocation_name=/opt/kandelo/bin/exec-child",
+    );
+    expect(result.stdout).toContain("program_invocation_short_name=exec-child");
 
     // exec-child prints env vars passed by exec-caller
     expect(result.stdout).toContain("FOO=bar");
@@ -45,6 +50,7 @@ describe("execve", () => {
       argv: ["fork-exec"],
       timeout: 15_000,
       execPrograms,
+      useDefaultRootfs: false,
     });
 
     // Parent exits 0

libc/musl-overlay/src/env/__libc_start_main.c

@@ -31,6 +31,7 @@ int __init_tp(void *);
 
 void __init_libc(char **envp, char *pn)
 {
+	size_t i;
 	__environ = envp;
 
 	/* On Wasm, there is no auxv, TLS, or secure-execution mode.
@@ -46,6 +47,7 @@ void __init_libc(char **envp, char *pn)
 
 	if (!pn) pn = "";
 	__progname = __progname_full = pn;
+	for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
 
 	/* Initialize the thread pointer for the main thread.
 	 * Set __wasm_thread_pointer to point at __wasm_tp_storage,

programs/exec-caller.c

@@ -8,7 +8,7 @@
 extern char **environ;
 
 int main(void) {
-    char *argv[] = {"exec-child", "hello", "world", NULL};
+    char *argv[] = {"/opt/kandelo/bin/exec-child", "hello", "world", NULL};
     char *envp[] = {"FOO=bar", "TEST=exec", NULL};
     execve("/bin/exec-child", argv, envp);
     /* If we get here, exec failed */

programs/exec-child.c

@@ -2,13 +2,17 @@
  * exec-child.c — Target program for exec tests.
  * Prints its argv and selected env vars to verify exec passed them correctly.
  */
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
+#include <errno.h>
 
 int main(int argc, char *argv[]) {
     printf("argc=%d\n", argc);
     for (int i = 0; i < argc; i++)
         printf("argv[%d]=%s\n", i, argv[i]);
+    printf("program_invocation_name=%s\n", program_invocation_name);
+    printf("program_invocation_short_name=%s\n", program_invocation_short_name);
 
     const char *foo = getenv("FOO");
     if (foo) printf("FOO=%s\n", foo);