Add libc direct tests for (get/set/unset)env functions

tests/pass-dep/libc/libc-env.rs

@@ -0,0 +1,96 @@
+//@ignore-target: windows # No libc
+//@compile-flags: -Zmiri-disable-isolation
+
+use std::ffi::CStr;
+
+fn test_getenv() {
+    let s = unsafe { libc::getenv(b"MIRI_ENV_VAR_TEST\0".as_ptr().cast()) };
+    assert!(!s.is_null());
+    let value = unsafe { CStr::from_ptr(s).to_str().unwrap() };
+    assert_eq!(value, "0");
+
+    // Get a non-existing environment variable
+    let s = unsafe { libc::getenv(b"MIRI_TEST_NONEXISTENT_VAR\0".as_ptr().cast()) };
+    assert!(s.is_null());
+
+    // Empty string should not crash
+    let s = unsafe { libc::getenv(b"\0".as_ptr().cast()) };
+    assert!(s.is_null());
+}
+
+fn test_setenv() {
+    // Set a new environment variable
+    let result = unsafe {
+        libc::setenv(b"MIRI_TEST_VAR\0".as_ptr().cast(), b"test_value\0".as_ptr().cast(), 1)
+    };
+    assert_eq!(result, 0);
+
+    // Verify it was set
+    let s = unsafe { libc::getenv(b"MIRI_TEST_VAR\0".as_ptr().cast()) };
+    assert!(!s.is_null());
+    let value = unsafe { CStr::from_ptr(s).to_str().unwrap() };
+    assert_eq!(value, "test_value");
+
+    // Test overwriting an existing variable
+    let result = unsafe {
+        libc::setenv(b"MIRI_TEST_VAR\0".as_ptr().cast(), b"new_value\0".as_ptr().cast(), 1)
+    };
+    assert_eq!(result, 0);
+
+    // Verify it was updated
+    let s = unsafe { libc::getenv(b"MIRI_TEST_VAR\0".as_ptr().cast()) };
+    assert!(!s.is_null());
+    let value = unsafe { CStr::from_ptr(s).to_str().unwrap() };
+    assert_eq!(value, "new_value");
+
+    // Test invalid parameters
+    let result = unsafe { libc::setenv(std::ptr::null(), b"value\0".as_ptr().cast(), 1) };
+    assert_eq!(result, -1);
+
+    let result = unsafe { libc::setenv(b"\0".as_ptr().cast(), b"value\0".as_ptr().cast(), 1) };
+    assert_eq!(result, -1);
+
+    let result =
+        unsafe { libc::setenv(b"INVALID=NAME\0".as_ptr().cast(), b"value\0".as_ptr().cast(), 1) };
+    assert_eq!(result, -1);
+}
+
+fn test_unsetenv() {
+    // Set a variable
+    let result = unsafe {
+        libc::setenv(b"MIRI_TEST_UNSET_VAR\0".as_ptr().cast(), b"to_be_unset\0".as_ptr().cast(), 1)
+    };
+    assert_eq!(result, 0);
+
+    // Verify it exists
+    let s = unsafe { libc::getenv(b"MIRI_TEST_UNSET_VAR\0".as_ptr().cast()) };
+    assert!(!s.is_null());
+
+    // Unset it
+    let result = unsafe { libc::unsetenv(b"MIRI_TEST_UNSET_VAR\0".as_ptr().cast()) };
+    assert_eq!(result, 0);
+
+    // Verify it was unset
+    let s = unsafe { libc::getenv(b"MIRI_TEST_UNSET_VAR\0".as_ptr().cast()) };
+    assert!(s.is_null());
+
+    // Test unsetting a non-existing variable (should succeed)
+    let result = unsafe { libc::unsetenv(b"MIRI_TEST_NONEXISTENT_VAR\0".as_ptr().cast()) };
+    assert_eq!(result, 0);
+
+    // Test invalid parameters
+    let result = unsafe { libc::unsetenv(std::ptr::null()) };
+    assert_eq!(result, -1);
+
+    let result = unsafe { libc::unsetenv(b"\0".as_ptr().cast()) };
+    assert_eq!(result, -1);
+
+    let result = unsafe { libc::unsetenv(b"INVALID=NAME\0".as_ptr().cast()) };
+    assert_eq!(result, -1);
+}
+
+fn main() {
+    test_getenv();
+    test_setenv();
+    test_unsetenv();
+}