Add build system scaffolding and libc headers

1 files changed, 58 insertions, 0 deletions

diff --git a/lib/libc/stdlib/setenv.c b/lib/libc/stdlib/setenv.c
new file mode 100644
index 00000000..1464fc1b
--- /dev/null
+++ b/lib/libc/stdlib/setenv.c
@@ -0,0 +1,58 @@
+#include <libc.h>
+#include <atomic.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern char **environ;
+
+int setenv(const char *var, const char *value, int overwrite)
+{
+	char **env = environ;
+	size_t var_len = strlen(var);
+
+	for (; *env; env++) {
+		char *eq = strchr(*env, '=');
+		if (eq && ((size_t)(eq - *env) == var_len) &&
+		    !strncmp(*env, var, var_len)) {
+			if (overwrite) {
+				size_t value_len = strlen(value);
+				char *new_env =
+					malloc(var_len + 1 + value_len + 1);
+				if (!new_env)
+					return -1;
+				memcpy(new_env, var, var_len);
+				new_env[var_len] = '=';
+				memcpy(new_env + var_len + 1, value,
+				       value_len + 1);
+				*env = new_env;
+			}
+			return 0;
+		}
+	}
+
+	size_t env_count = 0;
+	while (environ[env_count])
+		env_count++;
+
+	char **new_envp = realloc(environ, (env_count + 2) * sizeof(char *));
+	if (!new_envp)
+		return -1;
+
+	size_t value_len = strlen(value);
+	char *new_var = malloc(var_len + 1 + value_len + 1);
+	if (!new_var)
+		return -1;
+
+	memcpy(new_var, var, var_len);
+	new_var[var_len] = '=';
+	memcpy(new_var + var_len + 1, value, value_len + 1);
+
+	new_envp[env_count] = new_var;
+	new_envp[env_count + 1] = NULL;
+	LIBC_LOCK(libc.lock.environ);
+	environ = new_envp;
+	LIBC_UNLOCK(libc.lock.environ);
+	libc.flags |= LIBC_ENVP_TOUCHED;
+
+	return 0;
+}