3 files changed, 63 insertions, 0 deletions
diff --git a/libc-bottom-half/crt/crt1-command.c b/libc-bottom-half/crt/crt1-command.c
new file mode 100644
index 0000000..fb9ee71
--- /dev/null
+++ b/libc-bottom-half/crt/crt1-command.c
@@ -0,0 +1,53 @@
+#ifdef _REENTRANT
+#include <stdatomic.h>
+extern void __wasi_init_tp(void);
+#endif
+#include <wasi/api.h>
+extern void __wasm_call_ctors(void);
+extern int __main_void(void);
+extern void __wasm_call_dtors(void);
+
+__attribute__((export_name("_start")))
+void _start(void) {
+    // Commands should only be called once per instance. This simple check
+    // ensures that the `_start` function isn't started more than once.
+    //
+    // We use `volatile` here to prevent the store to `started` from being
+    // sunk past any subsequent code, and to prevent any compiler from
+    // optimizing based on the knowledge that `_start` is the program
+    // entrypoint.
+#ifdef _REENTRANT
+    static volatile _Atomic int started = 0;
+    int expected = 0;
+    if (!atomic_compare_exchange_strong(&started, &expected, 1)) {
+	__builtin_trap();
+    }
+#else
+    static volatile int started = 0;
+    if (started != 0) {
+	__builtin_trap();
+    }
+    started = 1;
+#endif
+
+#ifdef _REENTRANT
+	__wasi_init_tp();
+#endif
+
+    // The linker synthesizes this to call constructors.
+    __wasm_call_ctors();
+
+    // Call `__main_void` which will either be the application's zero-argument
+    // `__main_void` function or a libc routine which obtains the command-line
+    // arguments and calls `__main_argv_argc`.
+    int r = __main_void();
+
+    // Call atexit functions, destructors, stdio cleanup, etc.
+    __wasm_call_dtors();
+
+    // If main exited successfully, just return, otherwise call
+    // `__wasi_proc_exit`.
+    if (r != 0) {
+        __wasi_proc_exit(r);
+    }
+}
diff --git a/libc-bottom-half/crt/crt1-reactor.c b/libc-bottom-half/crt/crt1-reactor.c
new file mode 100644
index 0000000..f507c9e
--- /dev/null
+++ b/libc-bottom-half/crt/crt1-reactor.c
@@ -0,0 +1,7 @@
+extern void __wasm_call_ctors(void);
+
+__attribute__((export_name("_initialize")))
+void _initialize(void) {
+    // The linker synthesizes this to call constructors.
+    __wasm_call_ctors();
+}
diff --git a/libc-bottom-half/crt/crt1.c b/libc-bottom-half/crt/crt1.c
new file mode 100644
index 0000000..cbbe073
--- /dev/null
+++ b/libc-bottom-half/crt/crt1.c
@@ -0,0 +1,3 @@
+// We compile a plain crt1.o for toolchain compatibility, but it's
+// identical to crt1-command.o.
+#include "crt1-command.c"