tests: posix: c_lib_ext: add tests for getsubopt()

Add tests for getsubopt().

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

tests/posix/c_lib_ext/src/getsubopt.c

@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2025 Tenstorrent AI ULC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/ztest.h>
+
+#include <stdlib.h>
+
+extern int getsubopt(char **optionp, char *const *keylistp, char **valuep);
+
+ZTEST(posix_c_lib_ext, test_getsubopt)
+{
+	char *value;
+	char *option;
+	char buf[32];
+
+	enum opte {
+		RO_OPTION,
+		RW_OPTION,
+		READ_SIZE_OPTION,
+		WRITE_SIZE_OPTION,
+		EMBEDDED_EQ_OPTION,
+	};
+
+	static char *key_list[] = {
+		[RO_OPTION] = "ro",
+		[RW_OPTION] = "rw",
+		[READ_SIZE_OPTION] = "rsize",
+		[WRITE_SIZE_OPTION] = "wsize",
+		[EMBEDDED_EQ_OPTION] = "equal",
+		NULL,
+	};
+
+	static char *empty_key_list[] = {
+		NULL,
+	};
+
+	/* degenerate cases */
+	zexpect_equal(-1, getsubopt(NULL, NULL, NULL));
+	zexpect_equal(-1, getsubopt(NULL, NULL, &value));
+	zexpect_equal(-1, getsubopt(NULL, key_list, NULL));
+	zexpect_equal(-1, getsubopt(NULL, key_list, &value));
+	zexpect_equal(-1, getsubopt(&option, NULL, NULL));
+	zexpect_equal(-1, getsubopt(&option, NULL, &value));
+
+	/* iterate over valuep being NULL and valid */
+	for (size_t j = 0; j < 2; ++j) {
+		char **valuep = (j == 0) ? NULL : &value;
+
+		/* empty options string */
+		memset(buf, 0, sizeof(buf));
+		option = buf;
+		value = (char *)0x4242;
+		zexpect_equal(-1, getsubopt(&option, key_list, valuep));
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		/* empty key list */
+		strcpy(buf, "ro,rsize=512,equal=1=2,rw");
+		option = buf;
+		value = (char *)0x4242;
+		zexpect_equal(-1, getsubopt(&option, empty_key_list, valuep));
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		strcpy(buf, "ro,rsize=512,equal=1=2,rw");
+		option = buf;
+		value = (char *)0x4242;
+		zexpect_equal(RO_OPTION, getsubopt(&option, key_list, valuep));
+		zexpect_equal(option, &buf[strlen("ro,")]);
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		value = (char *)0x4242;
+		zexpect_equal(READ_SIZE_OPTION, getsubopt(&option, key_list, valuep));
+		zexpect_equal(option, &buf[strlen("ro,rsize=512,")]);
+		if (valuep != NULL) {
+			zexpect_str_equal(value, "512");
+		}
+
+		value = (char *)0x4242;
+		zexpect_equal(EMBEDDED_EQ_OPTION, getsubopt(&option, key_list, valuep));
+		zexpect_equal(option, &buf[strlen("ro,rsize=512,equal=1=2,")]);
+		if (valuep != NULL) {
+			zexpect_str_equal(value, "1=2");
+		}
+
+		value = (char *)0x4242;
+		zexpect_equal(RW_OPTION, getsubopt(&option, key_list, valuep));
+		zexpect_equal(option, &buf[strlen("ro,rsize=512,equal=1=2,rw")]);
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		value = (char *)0x4242;
+		zexpect_equal(getsubopt(&option, key_list, valuep), -1);
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		strcpy(buf, "oops");
+		option = buf;
+		value = (char *)0x4242;
+		zexpect_equal(getsubopt(&option, key_list, valuep), -1);
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		/* some corner cases */
+		strcpy(buf, ",rsize=,");
+		option = buf;
+		value = (char *)0x4242;
+		zexpect_equal(-1, getsubopt(&option, key_list, valuep));
+		zexpect_equal(option, &buf[strlen(",")]);
+		if (valuep != NULL) {
+			zexpect_equal(value, NULL);
+		}
+
+		value = (char *)0x4242;
+		zexpect_equal(READ_SIZE_OPTION, getsubopt(&option, key_list, valuep));
+		zexpect_equal(option, &buf[strlen(",rsize=,")]);
+		if (valuep != NULL) {
+			zexpect_str_equal(value, "");
+		}
+	}
+}