feat: add eintrtarget and envprint

user/envprint.c

@@ -0,0 +1,84 @@
+#include "ulib.h"
+
+/*
+ * Live ring-3 proof for the real environment-variable subsystem (sched.h's
+ * Thread.env, syscall.c's sysGetEnv/sysSetEnv/sysUnsetEnv, shell.c's
+ * `export`/`env`/`unset` builtins and `$NAME` expansion) -- loaded on demand by
+ * the real interactive shell (kmain.c's envDriverThread types
+ * "export GREETING=frostbyte" then "envprint" at it, the same injected-
+ * keystroke mechanism every shell-driven demo above already uses), never
+ * boot-spawned, the same "no kmain.c spawnUser call, only /bin/NAME
+ * resolved by the shell's own fallback" shape jobctlfg.c/hcat.c/pipecat.c
+ * already established.
+ *
+ * Proves inheritance first (this process never called userSetEnv itself
+ * before the first check -- whatever it sees came only from
+ * threadCreateUser's own initialEnv copying the shell's table at spawn
+ * time), then proves this process's OWN later userSetEnv is visible to
+ * itself immediately, then proves userUnsetEnv actually removes the entry
+ * (a following userGetEnv on the same name fails) and that unsetting a
+ * name that was never set is still a no-op success, not an error. The
+ * other half of the isolation guarantee --  that
+ * this process's own mutation can never reach back into the PARENT
+ * shell's copy -- is proven by envDriverThread itself: it types a plain
+ * "env" at the shell AFTER this process has already exited and checks
+ * that the shell still reports the ORIGINAL "frostbyte" value, not
+ * "child-mutated" (mirrors cwdtest.c's own post-userWait
+ * parent-cwd-unaffected check, just driven through the shell instead of a
+ * direct userWait).
+ */
+
+int main(void)
+{
+    print("envprint: start, pid=");
+    printDec(userGetpid());
+    print("\n");
+
+    char value[32];
+    long len = userGetEnv("GREETING", value, sizeof(value));
+    if (len < 0) {
+        print("envprint: FAIL missing inherited GREETING\n");
+        return 1;
+    }
+    print("envprint: inherited-ok GREETING=");
+    print(value);
+    print("\n");
+
+    if (userGetEnv("NO_SUCH_VAR", value, sizeof(value)) >= 0) {
+        print("envprint: FAIL unset variable returned a value\n");
+        return 1;
+    }
+
+    if (userSetEnv("GREETING", "child-mutated") != 0) {
+        print("envprint: FAIL setenv\n");
+        return 1;
+    }
+    len = userGetEnv("GREETING", value, sizeof(value));
+    if (len < 0) {
+        print("envprint: FAIL read back own setenv\n");
+        return 1;
+    }
+    print("envprint: self-set-ok GREETING=");
+    print(value);
+    print("\n");
+
+    if (userUnsetEnv("GREETING") != 0) {
+        print("envprint: FAIL unset\n");
+        return 1;
+    }
+    if (userGetEnv("GREETING", value, sizeof(value)) >= 0) {
+        print("envprint: FAIL unset did not remove variable\n");
+        return 1;
+    }
+    print("envprint: unset-ok\n");
+
+    /* Real unsetenv(3) is a no-op success on a name that was never set --
+       this must NOT be confused with a "not found" error. */
+    if (userUnsetEnv("NO_SUCH_VAR_EVER") != 0) {
+        print("envprint: FAIL unset-missing should be a no-op success\n");
+        return 1;
+    }
+    print("envprint: unset-missing-ok\n");
+
+    return 0;
+}