tests/unit: add test-envlist covering setenv/unsetenv name matching

util/envlist had no test coverage. Add tests/unit/test-envlist
exercising the public envlist API and pinning down the prefix-match
hazard fixed in the previous commit:

  - envlist_unsetenv("FOO") must not remove an entry named "FOOBAR";
  - envlist_setenv("FOO=...") must not replace an existing "FOOBAR=..."
    entry placed earlier in the list (envlist_setenv() inserts at the
    head, so the first prefix match wins under the old strncmp rule).

Also cover the rest of the contract: head-insertion order observed
through envlist_to_environ(), replacement of an existing variable,
the count argument of envlist_to_environ(), and the documented EINVAL
paths (NULL inputs, setenv without '=', unsetenv with '=').

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20260520212628.479772-3-den@openvz.org
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 05221c600a5f3ef657d71aeaea632c5f1bab3a2d)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

2 files changed, 197 insertions, 0 deletions

diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index d5248ae51d..1a85f85d18 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -48,6 +48,7 @@ tests = {
   'test-qapi-util': [],
   'test-interval-tree': [],
   'test-fifo': [],
+  'test-envlist': [],
 }
 
 if have_system or have_tools
diff --git a/tests/unit/test-envlist.c b/tests/unit/test-envlist.c
new file mode 100644
index 0000000000..53813dd4de
--- /dev/null
+++ b/tests/unit/test-envlist.c
@@ -0,0 +1,196 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * envlist tests
+ *
+ * Copyright 2026 Virtuozzo International GmbH
+ *
+ * Authors:
+ *  Denis V. Lunev <den@openvz.org>
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/envlist.h"
+
+static void free_environ(char **env)
+{
+    char **p;
+
+    for (p = env; *p != NULL; p++) {
+        g_free(*p);
+    }
+    g_free(env);
+}
+
+static const char *find_env(char **env, const char *name)
+{
+    size_t name_len = strlen(name);
+    char **p;
+
+    for (p = env; *p != NULL; p++) {
+        if (strncmp(*p, name, name_len) == 0 && (*p)[name_len] == '=') {
+            return *p + name_len + 1;
+        }
+    }
+    return NULL;
+}
+
+static void test_envlist_basic(void)
+{
+    envlist_t *el = envlist_create();
+    char **env;
+    size_t count;
+
+    /* empty list */
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 0);
+    g_assert_null(env[0]);
+    free_environ(env);
+
+    /* add */
+    g_assert_cmpint(envlist_setenv(el, "A=1"), ==, 0);
+    g_assert_cmpint(envlist_setenv(el, "B=2"), ==, 0);
+
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 2);
+    g_assert_cmpstr(find_env(env, "A"), ==, "1");
+    g_assert_cmpstr(find_env(env, "B"), ==, "2");
+    free_environ(env);
+
+    /* replace */
+    g_assert_cmpint(envlist_setenv(el, "A=42"), ==, 0);
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 2);
+    g_assert_cmpstr(find_env(env, "A"), ==, "42");
+    g_assert_cmpstr(find_env(env, "B"), ==, "2");
+    free_environ(env);
+
+    /* unset existing */
+    g_assert_cmpint(envlist_unsetenv(el, "A"), ==, 0);
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 1);
+    g_assert_null(find_env(env, "A"));
+    g_assert_cmpstr(find_env(env, "B"), ==, "2");
+    free_environ(env);
+
+    /* unset non-existing is a no-op success */
+    g_assert_cmpint(envlist_unsetenv(el, "NOPE"), ==, 0);
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 1);
+    free_environ(env);
+
+    envlist_free(el);
+}
+
+/*
+ * envlist_setenv() inserts at the head; envlist_to_environ() walks
+ * head-to-tail, so the last setenv comes out first.
+ */
+static void test_envlist_head_insertion_order(void)
+{
+    envlist_t *el = envlist_create();
+    char **env;
+    size_t count;
+
+    g_assert_cmpint(envlist_setenv(el, "A=1"), ==, 0);
+    g_assert_cmpint(envlist_setenv(el, "B=2"), ==, 0);
+    g_assert_cmpint(envlist_setenv(el, "C=3"), ==, 0);
+
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 3);
+    g_assert_cmpstr(env[0], ==, "C=3");
+    g_assert_cmpstr(env[1], ==, "B=2");
+    g_assert_cmpstr(env[2], ==, "A=1");
+    g_assert_null(env[3]);
+
+    free_environ(env);
+    envlist_free(el);
+}
+
+static void test_envlist_einval(void)
+{
+    envlist_t *el = envlist_create();
+
+    /* NULL list */
+    g_assert_cmpint(envlist_setenv(NULL, "A=1"), ==, EINVAL);
+    g_assert_cmpint(envlist_unsetenv(NULL, "A"), ==, EINVAL);
+
+    /* NULL string */
+    g_assert_cmpint(envlist_setenv(el, NULL), ==, EINVAL);
+    g_assert_cmpint(envlist_unsetenv(el, NULL), ==, EINVAL);
+
+    /* setenv: missing '=' */
+    g_assert_cmpint(envlist_setenv(el, "NOEQ"), ==, EINVAL);
+
+    /* unsetenv: name must not contain '=' */
+    g_assert_cmpint(envlist_unsetenv(el, "A=B"), ==, EINVAL);
+
+    envlist_free(el);
+}
+
+/*
+ * Regression: envlist_unsetenv("FOO") must not remove an entry named
+ * "FOOBAR" -- the previous strncmp(entry, name, strlen(name)) lookup
+ * prefix-matched. To trigger the bug, the longer-named entry has to
+ * be ahead of the target in the list: envlist_setenv() inserts at
+ * the head, so we add FOO first and FOOBAR last.
+ */
+static void test_envlist_unsetenv_no_prefix_match(void)
+{
+    envlist_t *el = envlist_create();
+    char **env;
+    size_t count;
+
+    g_assert_cmpint(envlist_setenv(el, "FOO=y"), ==, 0);
+    g_assert_cmpint(envlist_setenv(el, "FOOBAR=x"), ==, 0);
+
+    g_assert_cmpint(envlist_unsetenv(el, "FOO"), ==, 0);
+
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 1);
+    g_assert_cmpstr(find_env(env, "FOOBAR"), ==, "x");
+    g_assert_null(find_env(env, "FOO"));
+
+    free_environ(env);
+    envlist_free(el);
+}
+
+/*
+ * envlist_setenv() must not replace a prior FOOBAR=... entry when
+ * setting FOO=... The pre-fix code happened to be safe here only
+ * because it included the trailing '=' byte in its strncmp length;
+ * this test pins down the post-fix contract that the name boundary
+ * is a property of the entry, not of the encoded form.
+ */
+static void test_envlist_setenv_no_prefix_match(void)
+{
+    envlist_t *el = envlist_create();
+    char **env;
+    size_t count;
+
+    g_assert_cmpint(envlist_setenv(el, "FOOBAR=x"), ==, 0);
+    g_assert_cmpint(envlist_setenv(el, "FOO=y"), ==, 0);
+
+    env = envlist_to_environ(el, &count);
+    g_assert_cmpuint(count, ==, 2);
+    g_assert_cmpstr(find_env(env, "FOOBAR"), ==, "x");
+    g_assert_cmpstr(find_env(env, "FOO"), ==, "y");
+
+    free_environ(env);
+    envlist_free(el);
+}
+
+int main(int argc, char *argv[])
+{
+    g_test_init(&argc, &argv, NULL);
+
+    g_test_add_func("/envlist/basic", test_envlist_basic);
+    g_test_add_func("/envlist/head_insertion_order",
+                    test_envlist_head_insertion_order);
+    g_test_add_func("/envlist/einval", test_envlist_einval);
+    g_test_add_func("/envlist/unsetenv_no_prefix_match",
+                    test_envlist_unsetenv_no_prefix_match);
+    g_test_add_func("/envlist/setenv_no_prefix_match",
+                    test_envlist_setenv_no_prefix_match);
+
+    return g_test_run();
+}