My guess is that in your V8ContextCreate function you also need a temporary
HandleScope before you can make a global out of the context:
v8::HandleScope handle_scope(engine->isolate);
On Mon, Nov 2, 2020 at 10:36 AM Marco Bambini <marco.bamb...@gmail.com>
wrote:
> Dear All,
> I am a C developer quite new to v8 (I have limited c++ knowledge).
> Sorry if I ask very basic questions.
>
> I have a C application that need to execute some js code in different
> times preserving the same context.
>
> My code looks like:
> *Header file*
> *=========*
> #ifdef __cplusplus
> extern "C" {
> #endif
> #include <stdbool.h>
>
> typedef struct V8Engine V8Engine;
> typedef struct V8Context V8Context;
> typedef struct V8Value V8Value;
>
> V8Engine* V8EngineInit (const char *path);
> void V8EngineFree (V8Engine *engine);
> V8Context* V8ContextCreate (V8Engine *engine);
> void V8ContextFree (V8Context *context);
> V8Value* V8ExecuteScript (V8Context *context, const char *script);
> bool V8ValueIsError (V8Value *value);
>
> #ifdef __cplusplus
>
> }
>
> #endif
>
> #endif
>
>
>
> *C++ file*
> *======*
> #include "libplatform/libplatform.h"
> #include "v8.h"
> #include "c8.h"
>
> struct V8Engine {
> std::unique_ptr<v8::Platform> platform;
> v8::Isolate::CreateParams create_params;
> v8::Isolate *isolate;
> v8::Isolate::Scope *isolate_scope;
>
> };
>
> struct V8Context {
> V8Engine *engine;
> v8::Global<v8::Context> *context;
> };
>
> struct V8Value {
>
> };
>
>
>
> // MARK: -
>
> extern "C" {
>
> V8Engine* V8EngineInit (const char *path) {
> V8Engine *engine = (V8Engine *)calloc(1, sizeof(V8Engine));
> if (!engine) return nullptr;
>
> // Initialize V8
> v8::V8::InitializeICUDefaultLocation(path);
> v8::V8::InitializeExternalStartupData(path);
> engine->platform = v8::platform::NewDefaultPlatform();
>
> v8::V8::InitializePlatform(engine->platform.get());
> v8::V8::Initialize();
>
> engine->create_params.array_buffer_allocator =
> v8::ArrayBuffer::Allocator::NewDefaultAllocator();
> engine->isolate = v8::Isolate::New(engine->create_params);
> engine->isolate_scope = new v8::Isolate::Scope(engine->isolate);
>
> return engine;
> }
>
>
> void V8EngineFree (V8Engine *engine) {
> if (engine == NULL) return;
>
> if (engine->isolate_scope) {
> delete engine->isolate_scope;
> }
>
> if (engine->isolate) {
> engine->isolate->Dispose();
> }
>
> v8::V8::Dispose();
> v8::V8::ShutdownPlatform();
>
> if (engine->create_params.array_buffer_allocator) {
> delete engine->create_params.array_buffer_allocator;
> }
>
> engine->~V8Engine();
> free(engine);
> }
>
>
>
> V8Context* V8ContextCreate (V8Engine *engine) {
> V8Context *instance = (V8Context *)calloc(1, sizeof(V8Context));
> if (!instance) return nullptr;
>
> instance->engine = engine;
> v8::Local<v8::Context> local_context =
> v8::Context::New(engine->isolate);
> instance->context = new v8::Global<v8::Context>(engine->isolate,
> local_context);
>
> return instance;
> }
>
> void V8ContextFree (V8Context *context) {
> delete context->context;
> context->~V8Context();
> free(context);
> }
>
>
>
> V8Value* V8ExecuteScript (V8Context *instance, const char *script) {
> // Create a stack-allocated handle scope
> v8::HandleScope handle_scope(instance->engine->isolate);
>
> // Enter the context for compiling and running the script
> v8::Local<v8::Context>
> context(instance->context->Get(instance->engine->isolate));
> v8::Context::Scope context_scope(context);
>
> {
> // Create a string containing the JavaScript source code
> v8::Local<v8::String> source =
> v8::String::NewFromUtf8(instance->engine->isolate, script,
> v8::NewStringType::kNormal).ToLocalChecked();
>
> // Compile the source code
> v8::Local<v8::Script> script = v8::Script::Compile(context,
> source).ToLocalChecked();
>
> // Run the script to get the result
> v8::Local<v8::Value> result =
> script->Run(context).ToLocalChecked();
>
> // Convert the result to an UTF8 string and print it
> v8::String::Utf8Value utf8(instance->engine->isolate, result);
> printf("%s\n", *utf8);
> }
>
> return nullptr;
> }
>
>
>
> bool V8ValueIsError (V8Value *value) {
> return false;
> }
>
> }
>
> *// main C file*
> *==========*
> int main (int argc, char* argv[]) {
> V8Engine *vm = V8EngineInit(argv[0]);
> V8Context *context = V8ContextCreate(vm);
>
> const char *script1 = " function js_add_elements(var1, var2) { \
> var var3 = parseInt(var1) +
> parseInt(var2); \
> var result = 'Addition of ' + var1 + ' and
> ' + var2 + ' results ' + var3; \
> return result; \
> };";
> const char *script2 = "js_add_elements(2, 3);";
> const char *script3 = "js_add_elements(4, 5);";
>
> V8ExecuteScript(context, script1);
> V8ExecuteScript(context, script2);
> V8ExecuteScript(context, script3);
>
> V8ContextFree(context);
> V8EngineFree(vm);
> }
>
> When I run this code this error is printed on console:
>
> *#*
> *# Fatal error in v8::HandleScope::CreateHandle()*
> *# Cannot create a handle without a HandleScope*
> *#*
>
> on the line
> v8::Local<v8::Context> local_context = v8::Context::New(engine->isolate);
>
> in
> V8Context* V8ContextCreate (V8Engine *engine)
>
> Please let me know what I am doing wrong (a fixed sample code would be
> extremely useful).
>
> Thanks a lot,
> Marco Bambini
>
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