Update Emscripten API layout; expose inner parts to to C API; add test

lib/emscripten/src/lib.rs

@@ -325,6 +325,61 @@ impl<'a> EmscriptenData<'a> {
     }
 }
 
+/// Call the global constructors for C++ and set up the emscripten environment.
+///
+/// Note that this function does not completely set up Emscripten to be called.
+/// before calling this function, please initialize `Ctx::data` with a pointer
+/// to [`EmscriptenData`].
+pub fn set_up_emscripten(instance: &mut Instance) -> CallResult<()> {
+    // ATINIT
+    // (used by C++)
+    if let Ok(_func) = instance.dyn_func("globalCtors") {
+        instance.call("globalCtors", &[])?;
+    }
+
+    if let Ok(_func) = instance.dyn_func("___emscripten_environ_constructor") {
+        instance.call("___emscripten_environ_constructor", &[])?;
+    }
+    Ok(())
+}
+
+/// Call the main function in emscripten, assumes that the emscripten state is
+/// set up.
+///
+/// If you don't want to set it up yourself, consider using [`run_emscripten_instance`].
+pub fn emscripten_call_main(instance: &mut Instance, path: &str, args: &[&str]) -> CallResult<()> {
+    let (func_name, main_func) = match instance.dyn_func("_main") {
+        Ok(func) => Ok(("_main", func)),
+        Err(_e) => match instance.dyn_func("main") {
+            Ok(func) => Ok(("main", func)),
+            Err(e) => Err(e),
+        },
+    }?;
+    let num_params = main_func.signature().params().len();
+    let _result = match num_params {
+        2 => {
+            let mut new_args = vec![path];
+            new_args.extend(args);
+            let (argc, argv) = store_module_arguments(instance.context_mut(), new_args);
+            instance.call(
+                func_name,
+                &[Value::I32(argc as i32), Value::I32(argv as i32)],
+            )?;
+        }
+        0 => {
+            instance.call(func_name, &[])?;
+        }
+        _ => {
+            return Err(CallError::Resolve(ResolveError::ExportWrongType {
+                name: "main".to_string(),
+            }))
+        }
+    };
+
+    Ok(())
+}
+
+/// Top level function to execute emscripten
 pub fn run_emscripten_instance(
     _module: &Module,
     instance: &mut Instance,
@@ -338,15 +393,7 @@ pub fn run_emscripten_instance(
     let data_ptr = &mut data as *mut _ as *mut c_void;
     instance.context_mut().data = data_ptr;
 
-    // ATINIT
-    // (used by C++)
-    if let Ok(_func) = instance.dyn_func("globalCtors") {
-        instance.call("globalCtors", &[])?;
-    }
-
-    if let Ok(_func) = instance.dyn_func("___emscripten_environ_constructor") {
-        instance.call("___emscripten_environ_constructor", &[])?;
-    }
+    set_up_emscripten(instance)?;
 
     // println!("running emscripten instance");
 
@@ -356,33 +403,7 @@ pub fn run_emscripten_instance(
         //let (argc, argv) = store_module_arguments(instance.context_mut(), args);
         instance.call(&ep, &[Value::I32(arg as i32)])?;
     } else {
-        let (func_name, main_func) = match instance.dyn_func("_main") {
-            Ok(func) => Ok(("_main", func)),
-            Err(_e) => match instance.dyn_func("main") {
-                Ok(func) => Ok(("main", func)),
-                Err(e) => Err(e),
-            },
-        }?;
-        let num_params = main_func.signature().params().len();
-        let _result = match num_params {
-            2 => {
-                let mut new_args = vec![path];
-                new_args.extend(args);
-                let (argc, argv) = store_module_arguments(instance.context_mut(), new_args);
-                instance.call(
-                    func_name,
-                    &[Value::I32(argc as i32), Value::I32(argv as i32)],
-                )?;
-            }
-            0 => {
-                instance.call(func_name, &[])?;
-            }
-            _ => {
-                return Err(CallError::Resolve(ResolveError::ExportWrongType {
-                    name: "main".to_string(),
-                }))
-            }
-        };
+        emscripten_call_main(instance, path, &args)?;
     }
 
     // TODO atexit for emscripten

lib/runtime-c-api/src/import/emscripten.rs

@@ -1,10 +1,11 @@
 //! Functions and types for dealing with Emscripten imports
 
 use super::*;
-use crate::module::wasmer_module_t;
+use crate::{get_slice_checked, instance::wasmer_instance_t, module::wasmer_module_t};
+
 use std::ptr;
 use wasmer_emscripten::EmscriptenGlobals;
-use wasmer_runtime::Module;
+use wasmer_runtime::{Instance, Module};
 
 /// Type used to construct an import_object_t with Emscripten imports.
 #[repr(C)]
@@ -40,9 +41,88 @@ pub unsafe extern "C" fn wasmer_emscripten_destroy_emscripten_globals(
     let _ = Box::from_raw(globals);
 }
 
+/// Execute global constructors (required if the module is compiled from C++)
+/// and sets up the internal environment.
+///
+/// This function sets the data pointer in the same way that
+/// [`wasmer_instance_context_data_set`] does.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_set_up_emscripten(
+    instance: *mut wasmer_instance_t,
+    globals: *mut wasmer_emscripten_globals_t,
+) -> wasmer_result_t {
+    if globals.is_null() || instance.is_null() {
+        return wasmer_result_t::WASMER_ERROR;
+    }
+    let instance = &mut *(instance as *mut Instance);
+    instance.context_mut().data = globals as *mut c_void;
+    match wasmer_emscripten::set_up_emscripten(instance) {
+        Ok(_) => wasmer_result_t::WASMER_OK,
+        Err(e) => {
+            update_last_error(e);
+            wasmer_result_t::WASMER_ERROR
+        }
+    }
+}
+
+/// Convenience function for setting up arguments and calling the Emscripten
+/// main function.
+///
+/// WARNING:
+///
+/// Do not call this function on untrusted code when operating without
+/// additional sandboxing in place.
+/// Emscripten has access to many host system calls and therefore may do very
+/// bad things.
+#[no_mangle]
+pub unsafe extern "C" fn wasmer_emscripten_call_main(
+    instance: *mut wasmer_instance_t,
+    args: *const wasmer_byte_array,
+    args_len: c_uint,
+) -> wasmer_result_t {
+    if instance.is_null() || args.is_null() {
+        return wasmer_result_t::WASMER_ERROR;
+    }
+    let instance = &mut *(instance as *mut Instance);
+
+    let arg_list = get_slice_checked(args, args_len as usize);
+    let arg_process_result: Result<Vec<&str>, _> =
+        arg_list.iter().map(|arg| arg.as_str()).collect();
+    let arg_vec = match arg_process_result.as_ref() {
+        Ok(arg_vec) => arg_vec,
+        Err(err) => {
+            update_last_error(*err);
+            return wasmer_result_t::WASMER_ERROR;
+        }
+    };
+
+    let prog_name = if let Some(prog_name) = arg_vec.first() {
+        prog_name
+    } else {
+        update_last_error(CApiError {
+            msg: "First argument (program name) is required to execute Emscripten's main function"
+                .to_string(),
+        });
+        return wasmer_result_t::WASMER_ERROR;
+    };
+
+    match wasmer_emscripten::emscripten_call_main(instance, prog_name, &arg_vec[1..]) {
+        Ok(_) => wasmer_result_t::WASMER_OK,
+        Err(e) => {
+            update_last_error(e);
+            wasmer_result_t::WASMER_ERROR
+        }
+    }
+}
+
 /// Create a `wasmer_import_object_t` with Emscripten imports, use
 /// `wasmer_emscripten_get_emscripten_globals` to get a
 /// `wasmer_emscripten_globals_t` from a `wasmer_module_t`.
+///
+/// WARNING:
+///1
+/// This `import_object_t` contains thin-wrappers around host system calls.
+/// Do not use this to execute untrusted code without additional sandboxing.
 #[no_mangle]
 pub unsafe extern "C" fn wasmer_emscripten_generate_import_object(
     globals: *mut wasmer_emscripten_globals_t,

lib/runtime-c-api/tests/.gitignore

@@ -26,4 +26,5 @@ test-module-imports
 test-module-serialize
 test-tables
 test-validate
-test-wasi-import-object
+test-wasi-import-object
+test-emscripten-import-object

lib/runtime-c-api/tests/CMakeLists.txt

@@ -22,6 +22,11 @@ if (DEFINED WASI_TESTS)
     add_executable(test-wasi-import-object test-wasi-import-object.c)
 endif()
 
+if (DEFINED EMSCRIPTEN_TESTS)
+    add_executable(test-emscripten-import-object test-emscripten-import-object.c)
+endif()
+
+
 find_library(
     WASMER_LIB NAMES libwasmer_runtime_c_api.dylib libwasmer_runtime_c_api.so wasmer_runtime_c_api.dll
     PATHS ${CMAKE_SOURCE_DIR}/../../../target/release/
@@ -74,6 +79,12 @@ if (DEFINED WASI_TESTS)
     add_test(test-wasi-import-object test-wasi-import-object)
 endif()
 
+if (DEFINED EMSCRIPTEN_TESTS)
+    target_link_libraries(test-emscripten-import-object general ${WASMER_LIB})
+    target_compile_options(test-emscripten-import-object PRIVATE ${COMPILER_OPTIONS})
+    add_test(test-emscripten-import-object test-emscripten-import-object)
+endif()
+
 target_link_libraries(test-instantiate general ${WASMER_LIB})
 target_compile_options(test-instantiate PRIVATE ${COMPILER_OPTIONS})
 add_test(test-instantiate test-instantiate)

lib/runtime-c-api/tests/assets/emscripten_hello_world.c

@@ -0,0 +1,10 @@
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+        printf("Hello, world\n");
+        for ( int i = 0; i < argc; ++i ) {
+                printf("Arg %d: '%s'\n", i, argv[i]);
+        }
+        return 0;
+}
+

lib/runtime-c-api/tests/runtime_c_api_tests.rs

@@ -8,8 +8,10 @@ fn test_c_api() {
         ".",
         #[cfg(feature = "wasi")]
         "-DWASI_TESTS=ON",
+        #[cfg(feature = "emscripten")]
+        "-DEMSCRIPTEN_TESTS=ON",
     ];
-    // we use -f so it doesn't fail if the fiel doesn't exist
+    // we use -f so it doesn't fail if the file doesn't exist
     run_command("rm", project_tests_dir, vec!["-f", "CMakeCache.txt"]);
     run_command("cmake", project_tests_dir, cmake_args);
     run_command("make", project_tests_dir, vec!["-Wdev", "-Werror=dev"]);

lib/runtime-c-api/tests/test-emscripten-import-object.c

@@ -0,0 +1,235 @@
+#include <stdio.h>
+#include "../wasmer.h"
+#include <assert.h>
+#include <stdint.h>
+#include <string.h>
+
+static bool host_print_called = false;
+
+// Host function that will be imported into the Web Assembly Instance
+void host_print(const wasmer_instance_context_t *ctx, int32_t ptr, int32_t len)
+{
+    host_print_called = true;
+    const wasmer_memory_t *memory = wasmer_instance_context_memory(ctx, 0);
+    uint32_t mem_len = wasmer_memory_length(memory);
+    uint8_t *mem_bytes = wasmer_memory_data(memory);
+    printf("%.*s", len, mem_bytes + ptr);
+}
+
+// Use the last_error API to retrieve error messages
+void print_wasmer_error()
+{
+    int error_len = wasmer_last_error_length();
+    printf("Error len: `%d`\n", error_len);
+    char *error_str = malloc(error_len);
+    wasmer_last_error_message(error_str, error_len);
+    printf("Error str: `%s`\n", error_str);
+}
+
+// helper function to print byte array to stdout
+void print_byte_array(wasmer_byte_array *arr) {
+    for (int i = 0; i < arr->bytes_len; ++i) {
+        putchar(arr->bytes[i]);
+    }
+}
+
+int main()
+{
+    // Create a new func to hold the parameter and signature
+    // of our `host_print` host function
+    wasmer_value_tag params_sig[] = {WASM_I32, WASM_I32};
+    wasmer_value_tag returns_sig[] = {};
+    wasmer_import_func_t *func = wasmer_import_func_new((void (*)(void *)) host_print, params_sig, 2, returns_sig, 0);
+
+    // Create module name for our imports
+    // represented in bytes for UTF-8 compatability
+    const char *module_name = "env";
+    wasmer_byte_array module_name_bytes;
+    module_name_bytes.bytes = (const uint8_t *) module_name;
+    module_name_bytes.bytes_len = strlen(module_name);
+
+    // Define a function import
+    const char *import_name = "host_print";
+    wasmer_byte_array import_name_bytes;
+    import_name_bytes.bytes = (const uint8_t *) import_name;
+    import_name_bytes.bytes_len = strlen(import_name);
+    wasmer_import_t func_import;
+    func_import.module_name = module_name_bytes;
+    func_import.import_name = import_name_bytes;
+    func_import.tag = WASM_FUNCTION;
+    func_import.value.func = func;
+
+    // Define a memory import
+    const char *import_memory_name = "memory";
+    wasmer_byte_array import_memory_name_bytes;
+    import_memory_name_bytes.bytes = (const uint8_t *) import_memory_name;
+    import_memory_name_bytes.bytes_len = strlen(import_memory_name);
+    wasmer_import_t memory_import;
+    memory_import.module_name = module_name_bytes;
+    memory_import.import_name = import_memory_name_bytes;
+    memory_import.tag = WASM_MEMORY;
+    wasmer_memory_t *memory = NULL;
+    wasmer_limits_t descriptor;
+    descriptor.min = 256;
+    wasmer_limit_option_t max;
+    max.has_some = true;
+    max.some = 256;
+    descriptor.max = max;
+    wasmer_result_t memory_result = wasmer_memory_new(&memory, descriptor);
+    if (memory_result != WASMER_OK)
+    {
+        print_wasmer_error();
+    }
+    memory_import.value.memory = memory;
+
+    // Define a global import
+    const char *import_global_name = "__memory_base";
+    wasmer_byte_array import_global_name_bytes;
+    import_global_name_bytes.bytes = (const uint8_t *) import_global_name;
+    import_global_name_bytes.bytes_len = strlen(import_global_name);
+    wasmer_import_t global_import;
+    global_import.module_name = module_name_bytes;
+    global_import.import_name = import_global_name_bytes;
+    global_import.tag = WASM_GLOBAL;
+    wasmer_value_t val;
+    val.tag = WASM_I32;
+    val.value.I32 = 1024;
+    wasmer_global_t *global = wasmer_global_new(val, false);
+    global_import.value.global = global;
+
+    // Define a table import
+    const char *import_table_name = "table";
+    wasmer_byte_array import_table_name_bytes;
+    import_table_name_bytes.bytes = (const uint8_t *) import_table_name;
+    import_table_name_bytes.bytes_len = strlen(import_table_name);
+    wasmer_import_t table_import;
+    table_import.module_name = module_name_bytes;
+    table_import.import_name = import_table_name_bytes;
+    table_import.tag = WASM_TABLE;
+    wasmer_table_t *table = NULL;
+    wasmer_limits_t table_descriptor;
+    table_descriptor.min = 256;
+    wasmer_limit_option_t table_max;
+    table_max.has_some = true;
+    table_max.some = 256;
+    table_descriptor.max = table_max;
+    wasmer_result_t table_result = wasmer_table_new(&table, table_descriptor);
+    if (table_result != WASMER_OK)
+    {
+        print_wasmer_error();
+    }
+    table_import.value.table = table;
+
+
+    // Create arbitrary arguments for our program
+
+
+    // Read the Wasm file bytes.
+    FILE *file = fopen("assets/emscripten_hello_world.wasm", "r");
+    assert(file);
+    fseek(file, 0, SEEK_END);
+    long len = ftell(file);
+    uint8_t *bytes = malloc(len);
+    fseek(file, 0, SEEK_SET);
+    fread(bytes, 1, len, file);
+    fclose(file);
+
+    wasmer_module_t *module = NULL;
+    // Compile the WebAssembly module
+    wasmer_result_t compile_result = wasmer_compile(&module, bytes, len);
+    printf("Compile result:  %d\n", compile_result);
+
+    if (compile_result != WASMER_OK)
+    {
+        print_wasmer_error();
+    }
+
+    assert(compile_result == WASMER_OK);
+
+    // Set up data for Emscripten
+    wasmer_emscripten_globals_t *emscripten_globals = wasmer_emscripten_get_emscripten_globals(module);
+
+    if (!emscripten_globals)
+    {
+        print_wasmer_error();
+    }
+    assert(emscripten_globals);
+
+    // Create the Emscripten import object
+    wasmer_import_object_t *import_object =
+            wasmer_emscripten_generate_import_object(emscripten_globals);
+
+    // Create our imports
+    wasmer_import_t imports[] = {func_import, global_import, memory_import, table_import};
+    int imports_len = sizeof(imports) / sizeof(imports[0]);
+    // Add our imports to the import object
+    wasmer_import_object_extend(import_object, imports, imports_len);
+
+    // Instantiatoe the module with our import_object
+    wasmer_instance_t *instance = NULL;
+    wasmer_result_t instantiate_result = wasmer_module_import_instantiate(&instance, module, import_object);
+    printf("Instantiate result:  %d\n", instantiate_result);
+
+    if (instantiate_result != WASMER_OK)
+    {
+        print_wasmer_error();
+    }
+    assert(instantiate_result == WASMER_OK);
+
+    // Set up emscripten to be called
+    wasmer_result_t setup_result = wasmer_emscripten_set_up_emscripten(instance, emscripten_globals);
+
+    if (setup_result != WASMER_OK)
+    {
+        print_wasmer_error();
+    }
+
+
+    const char *emscripten_prog_name = "emscripten_test_program";
+    const char *emscripten_first_arg = "--help";
+    wasmer_byte_array args[] = {
+            { .bytes = (const uint8_t *) emscripten_prog_name,
+              .bytes_len = strlen(emscripten_prog_name) },
+            { .bytes = (const uint8_t *) emscripten_first_arg,
+              .bytes_len = strlen(emscripten_first_arg) }
+    };
+    int emscripten_argc = sizeof(args) / sizeof(args[0]);
+
+    wasmer_result_t main_result = wasmer_emscripten_call_main(instance, args, emscripten_argc);
+
+    printf("Main result:  %d\n", main_result);
+    assert(main_result == WASMER_OK);
+
+
+    wasmer_import_object_iter_t *func_iter = wasmer_import_object_iterate_functions(import_object);
+
+    puts("Functions in import object:");
+    while ( !wasmer_import_object_iter_at_end(func_iter) ) {
+            wasmer_import_t import;
+            wasmer_result_t result = wasmer_import_object_iter_next(func_iter, &import);
+            assert(result == WASMER_OK);
+
+            print_byte_array(&import.module_name);
+            putchar(' ');
+            print_byte_array(&import.import_name);
+            putchar('\n');
+
+            assert(import.tag == WASM_FUNCTION);
+            assert(import.value.func);
+            wasmer_import_object_imports_destroy(&import, 1);
+    }
+    wasmer_import_object_iter_destroy(func_iter);
+
+    // Use *_destroy methods to cleanup as specified in the header documentation
+    wasmer_emscripten_destroy_emscripten_globals(emscripten_globals);
+    wasmer_import_func_destroy(func);
+    wasmer_global_destroy(global);
+    wasmer_memory_destroy(memory);
+    wasmer_table_destroy(table);
+    wasmer_instance_destroy(instance);
+    wasmer_import_object_destroy(import_object);
+    wasmer_module_destroy(module);
+
+    return 0;
+}
+

lib/runtime-c-api/wasmer.h

@@ -14,6 +14,7 @@
 #endif
 #endif
 
+#define WASMER_EMSCRIPTEN_ENABLED
 #endif // WASMER_H_MACROS
 
 
@@ -74,6 +75,15 @@ typedef struct {
 
 } wasmer_module_t;
 
+typedef struct {
+
+} wasmer_instance_t;
+
+typedef struct {
+  const uint8_t *bytes;
+  uint32_t bytes_len;
+} wasmer_byte_array;
+
 #if defined(WASMER_EMSCRIPTEN_ENABLED)
 /**
  * Type used to construct an import_object_t with Emscripten imports.
@@ -94,11 +104,6 @@ typedef struct {
 
 } wasmer_export_descriptor_t;
 
-typedef struct {
-  const uint8_t *bytes;
-  uint32_t bytes_len;
-} wasmer_byte_array;
-
 /**
  * Opaque pointer to `NamedExportDescriptors`.
  */
@@ -191,10 +196,6 @@ typedef struct {
 
 typedef struct {
 
-} wasmer_instance_t;
-
-typedef struct {
-
 } wasmer_instance_context_t;
 
 typedef struct {
@@ -256,6 +257,23 @@ wasmer_result_t wasmer_compile(wasmer_module_t **module,
                                uint8_t *wasm_bytes,
                                uint32_t wasm_bytes_len);
 
+#if defined(WASMER_EMSCRIPTEN_ENABLED)
+/**
+ * Convenience function for setting up arguments and calling the Emscripten
+ * main function.
+ *
+ * WARNING:
+ *
+ * Do not call this function on untrusted code when operating without
+ * additional sandboxing in place.
+ * Emscripten has access to many host system calls and therefore may do very
+ * bad things.
+ */
+wasmer_result_t wasmer_emscripten_call_main(wasmer_instance_t *instance,
+                                            const wasmer_byte_array *args,
+                                            unsigned int args_len);
+#endif
+
 #if defined(WASMER_EMSCRIPTEN_ENABLED)
 /**
  * Destroy `wasmer_emscrpten_globals_t` created by
@@ -269,6 +287,11 @@ void wasmer_emscripten_destroy_emscripten_globals(wasmer_emscripten_globals_t *g
  * Create a `wasmer_import_object_t` with Emscripten imports, use
  * `wasmer_emscripten_get_emscripten_globals` to get a
  * `wasmer_emscripten_globals_t` from a `wasmer_module_t`.
+ *
+ * WARNING:
+ *1
+ * This `import_object_t` contains thin-wrappers around host system calls.
+ * Do not use this to execute untrusted code without additional sandboxing.
  */
 wasmer_import_object_t *wasmer_emscripten_generate_import_object(wasmer_emscripten_globals_t *globals);
 #endif
@@ -280,6 +303,18 @@ wasmer_import_object_t *wasmer_emscripten_generate_import_object(wasmer_emscript
 wasmer_emscripten_globals_t *wasmer_emscripten_get_emscripten_globals(const wasmer_module_t *module);
 #endif
 
+#if defined(WASMER_EMSCRIPTEN_ENABLED)
+/**
+ * Execute global constructors (required if the module is compiled from C++)
+ * and sets up the internal environment.
+ *
+ * This function sets the data pointer in the same way that
+ * [`wasmer_instance_context_data_set`] does.
+ */
+wasmer_result_t wasmer_emscripten_set_up_emscripten(wasmer_instance_t *instance,
+                                                    wasmer_emscripten_globals_t *globals);
+#endif
+
 /**
  * Gets export descriptor kind
  */

lib/runtime-c-api/wasmer.hh

@@ -14,6 +14,7 @@
 #endif
 #endif
 
+#define WASMER_EMSCRIPTEN_ENABLED
 #endif // WASMER_H_MACROS
 
 
@@ -61,6 +62,15 @@ struct wasmer_module_t {
 
 };
 
+struct wasmer_instance_t {
+
+};
+
+struct wasmer_byte_array {
+  const uint8_t *bytes;
+  uint32_t bytes_len;
+};
+
 #if defined(WASMER_EMSCRIPTEN_ENABLED)
 /// Type used to construct an import_object_t with Emscripten imports.
 struct wasmer_emscripten_globals_t {
@@ -77,11 +87,6 @@ struct wasmer_export_descriptor_t {
 
 };
 
-struct wasmer_byte_array {
-  const uint8_t *bytes;
-  uint32_t bytes_len;
-};
-
 /// Opaque pointer to `NamedExportDescriptors`.
 struct wasmer_export_descriptors_t {
 
@@ -162,10 +167,6 @@ struct wasmer_import_object_iter_t {
 
 };
 
-struct wasmer_instance_t {
-
-};
-
 struct wasmer_instance_context_t {
 
 };
@@ -223,6 +224,21 @@ wasmer_result_t wasmer_compile(wasmer_module_t **module,
                                uint8_t *wasm_bytes,
                                uint32_t wasm_bytes_len);
 
+#if defined(WASMER_EMSCRIPTEN_ENABLED)
+/// Convenience function for setting up arguments and calling the Emscripten
+/// main function.
+///
+/// WARNING:
+///
+/// Do not call this function on untrusted code when operating without
+/// additional sandboxing in place.
+/// Emscripten has access to many host system calls and therefore may do very
+/// bad things.
+wasmer_result_t wasmer_emscripten_call_main(wasmer_instance_t *instance,
+                                            const wasmer_byte_array *args,
+                                            unsigned int args_len);
+#endif
+
 #if defined(WASMER_EMSCRIPTEN_ENABLED)
 /// Destroy `wasmer_emscrpten_globals_t` created by
 /// `wasmer_emscripten_get_emscripten_globals`.
@@ -233,6 +249,11 @@ void wasmer_emscripten_destroy_emscripten_globals(wasmer_emscripten_globals_t *g
 /// Create a `wasmer_import_object_t` with Emscripten imports, use
 /// `wasmer_emscripten_get_emscripten_globals` to get a
 /// `wasmer_emscripten_globals_t` from a `wasmer_module_t`.
+///
+/// WARNING:
+///1
+/// This `import_object_t` contains thin-wrappers around host system calls.
+/// Do not use this to execute untrusted code without additional sandboxing.
 wasmer_import_object_t *wasmer_emscripten_generate_import_object(wasmer_emscripten_globals_t *globals);
 #endif
 
@@ -241,6 +262,16 @@ wasmer_import_object_t *wasmer_emscripten_generate_import_object(wasmer_emscript
 wasmer_emscripten_globals_t *wasmer_emscripten_get_emscripten_globals(const wasmer_module_t *module);
 #endif
 
+#if defined(WASMER_EMSCRIPTEN_ENABLED)
+/// Execute global constructors (required if the module is compiled from C++)
+/// and sets up the internal environment.
+///
+/// This function sets the data pointer in the same way that
+/// [`wasmer_instance_context_data_set`] does.
+wasmer_result_t wasmer_emscripten_set_up_emscripten(wasmer_instance_t *instance,
+                                                    wasmer_emscripten_globals_t *globals);
+#endif
+
 /// Gets export descriptor kind
 wasmer_import_export_kind wasmer_export_descriptor_kind(wasmer_export_descriptor_t *export_);