Could be a bug in valgrind, or a bug in V8. Getting a line number would be
helpful, along with the exact version of V8. At a quick glance, I don't see
any uninitialized variables
in DeclarationScope::CheckConflictingVarDeclarations.
On Thu, Jun 27, 2019 at 2:27 PM Austin Einter <austin.ein...@gmail.com>
wrote:
> I changed the line to
> v8::Local<v8::Context> context(instance->context->Get(instance->isolate));
>
> It is compiling also working fine.
>
> However when I execute this executable with valgrind, I get lot of
> "*Conditional
> jump or move depends on uninitialised value(s)*"
>
> One such conditional jump is given below.
>
> ==5158== Conditional jump or move depends on uninitialised value(s)
> ==5158== at 0x8F0868:
> v8::internal::DeclarationScope::CheckConflictingVarDeclarations() (in
> /home/user/mjse)
> ==5158== by 0x4D8F68:
> v8::internal::PreParser::PreParseFunction(v8::internal::AstRawString
> const*, v8::internal::FunctionKind,
> v8::internal::FunctionLiteral::FunctionType,
> v8::internal::DeclarationScope*, int*,
> v8::internal::ProducedPreparseData**, int) (in /home/user/mjse)
> ==5158== by 0x4B7935:
> v8::internal::Parser::SkipFunction(v8::internal::AstRawString const*,
> v8::internal::FunctionKind, v8::internal::FunctionLiteral::FunctionType,
> v8::internal::DeclarationScope*, int*, int*,
> v8::internal::ProducedPreparseData**) (in /home/user/mjse)
> ==5158== by 0x4AB715:
> v8::internal::Parser::ParseFunctionLiteral(v8::internal::AstRawString
> const*, v8::internal::Scanner::Location,
> v8::internal::FunctionNameValidity, v8::internal::FunctionKind, int,
> v8::internal::FunctionLiteral::FunctionType, v8::internal::LanguageMode,
> v8::internal::ZoneList<v8::internal::AstRawString const*>*) (in
> /home/user/mjse)
> ==5158== by 0x4D1EFA:
> v8::internal::ParserBase<v8::internal::Parser>::ParseHoistableDeclaration(int,
> v8::base::Flags<v8::internal::ParseFunctionFlag, int>,
> v8::internal::ZoneList<v8::internal::AstRawString const*>*, bool) (in
> /home/user/mjse)
> ==5158== by 0x4AA266:
> v8::internal::Parser::DoParseProgram(v8::internal::Isolate*,
> v8::internal::ParseInfo*) (in /home/user/mjse)
> ==5158== by 0x4A9958:
> v8::internal::Parser::ParseProgram(v8::internal::Isolate*,
> v8::internal::ParseInfo*) (in /home/user/mjse)
> ==5158== by 0x4D5759:
> v8::internal::parsing::ParseProgram(v8::internal::ParseInfo*,
> v8::internal::Isolate*) (in /home/user/mjse)
> ==5158== by 0x22A835: v8::internal::(anonymous
> namespace)::CompileToplevel(v8::internal::ParseInfo*,
> v8::internal::Isolate*, v8::internal::IsCompiledScope*) (in /home/user/mjse)
> ==5158== by 0x22C128:
> v8::internal::Compiler::GetSharedFunctionInfoForScript(v8::internal::Isolate*,
> v8::internal::Handle<v8::internal::String>,
> v8::internal::Compiler::ScriptDetails const&, v8::ScriptOriginOptions,
> v8::Extension*, v8::internal::ScriptData*,
> v8::ScriptCompiler::CompileOptions, v8::ScriptCompiler::NoCacheReason,
> v8::internal::NativesFlag) (in /home/user/mjse)
> ==5158== by 0x1F0EE4:
> v8::ScriptCompiler::CompileUnboundInternal(v8::Isolate*,
> v8::ScriptCompiler::Source*, v8::ScriptCompiler::CompileOptions,
> v8::ScriptCompiler::NoCacheReason) (in /home/user/mjse)
> ==5158== by 0x1F15D6:
> v8::ScriptCompiler::Compile(v8::Local<v8::Context>,
> v8::ScriptCompiler::Source*, v8::ScriptCompiler::CompileOptions,
> v8::ScriptCompiler::NoCacheReason) (in /home/user/mjse)
> ==5158==
>
>
> What could be the issue?
>
> Thanks
> Austin
>
>
>
>
> On Thu, Jun 27, 2019 at 5:34 PM Austin Einter <austin.ein...@gmail.com>
> wrote:
>
>> Thanks Ben. I followed your suggestion.
>> I added *v8::Global<v8::Context> *context; *member in instance structure.
>>
>> I put the code as below.
>>
>>
>>
>>
>>
>>
>> * if(instance->context == nullptr) { v8::Local<v8::Context>
>> context = v8::Context::New(instance->isolate); instance->context =
>> new v8::Global<v8::Context>(instance->isolate, context); }*
>>
>> * v8::Local<v8::Context> context(instance->isolate,
>> instance->context);*
>>
>> * For last line (in red) I am getting below compilation error.*
>>
>> error: no matching function for call to
>> ‘v8::Local<v8::Context>::Local(v8::Isolate*&, v8::Global<v8::Context>*&)’
>>
>> Please let me know what I need to do to avoid this error.
>>
>> Thanks
>> Austin
>>
>>
>> On Thu, Jun 27, 2019 at 2:09 PM Ben Noordhuis <i...@bnoordhuis.nl> wrote:
>>
>>> On Thu, Jun 27, 2019 at 5:05 AM Austin Einter <austin.ein...@gmail.com>
>>> wrote:
>>> >
>>> > Dear All
>>> > I am quite new to v8. I am a c developer, with limited c++ knowledge.
>>> Sorry if I ask very basic questions.
>>> >
>>> > I have a C application, that interacts with web servers. Gets
>>> javascript. Need to execute javascript.
>>> > Imagine a situation, where I get total 2 javascript files from server.
>>> >
>>> > js1.js
>>> >
>>> > function js_add_elements(var1, var2)
>>> > {
>>> > var var3 = parseInt(var1) + parseInt(var2);
>>> > var result = 'Addition of ' + var1 + ' and ' + var2 + ' results '
>>> + var3;
>>> > return result;
>>> > }
>>> >
>>> >
>>> > js2.js
>>> >
>>> > js_add_elements(2, 3);
>>> >
>>> >
>>> >
>>> > I have my c code as below.
>>> >
>>> > Header file
>>> > typedef struct
>>> > {
>>> > std::unique_ptr<v8::Platform> platform;
>>> > v8::Isolate::CreateParams create_params;
>>> > v8::Isolate *isolate;
>>> > v8::Isolate::Scope *isolate_scope;
>>> > }MJSEInstance;
>>> >
>>> > #ifdef __cplusplus
>>> > extern "C" {
>>> > #endif
>>> >
>>> > /**
>>> > * @brief Create MJSE instance
>>> > */
>>> > void *mjse_create_instance(char **argv);
>>> >
>>> > /**
>>> > * @brief Destroy MJSE instance
>>> > * @param instance -> MJSE instance
>>> > */
>>> > void mjse_destroy_instance(void *instance);
>>> >
>>> > /**
>>> > * @brief Executes a script
>>> > * @param minstance - MJSE instance
>>> > * @param jscript - the javascript
>>> > * @param scriptlen - Length of script
>>> > */
>>> > void mjse_execute_script(void *instance, char *jscript);
>>> >
>>> > #ifdef __cplusplus
>>> > }
>>> > #endif
>>> >
>>> > CPP File
>>> > #include <stdio.h>
>>> > #include <stdlib.h>
>>> > #include <string.h>
>>> > #include "include/libplatform/libplatform.h"
>>> > #include "include/v8.h"
>>> > #include "mjse.h"
>>> > #include "mjse_int.h"
>>> > #include <new>
>>> >
>>> > extern "C" {
>>> > using namespace v8;
>>> >
>>> > void *mjse_create_instance(char **argv)
>>> > {
>>> > MJSEInstance *instance = (MJSEInstance *)calloc(1,
>>> sizeof(MJSEInstance));
>>> >
>>> > v8::V8::InitializeICUDefaultLocation(argv[0]);
>>> > v8::V8::InitializeExternalStartupData(argv[0]);
>>> > instance->platform = v8::platform::NewDefaultPlatform();
>>> >
>>> > v8::V8::InitializePlatform(instance->platform.get());
>>> > v8::V8::Initialize();
>>> >
>>> > instance->create_params.array_buffer_allocator =
>>> v8::ArrayBuffer::Allocator::NewDefaultAllocator();
>>> > instance->isolate = v8::Isolate::New(instance->create_params);
>>> > instance->isolate_scope = new
>>> v8::Isolate::Scope(instance->isolate);
>>> >
>>> > return instance;
>>> > }
>>> >
>>> > void mjse_destroy_instance(void *minstance)
>>> > {
>>> > MJSEInstance *instance = (MJSEInstance *)minstance;
>>> >
>>> > if(instance == NULL)
>>> > return;
>>> >
>>> > if(instance->isolate_scope)
>>> > {
>>> > delete instance->isolate_scope;
>>> > }
>>> >
>>> > if(instance->isolate)
>>> > {
>>> > instance->isolate->Dispose();
>>> > }
>>> >
>>> > v8::V8::Dispose();
>>> > v8::V8::ShutdownPlatform();
>>> >
>>> > if(instance->create_params.array_buffer_allocator)
>>> > {
>>> > delete instance->create_params.array_buffer_allocator;
>>> > }
>>> >
>>> > instance->~MJSEInstance();
>>> > free(instance);
>>> > }
>>> >
>>> >
>>> > void mjse_execute_script(void *minstance, char *jscript)
>>> > {
>>> > MJSEInstance *instance = (MJSEInstance *)minstance;
>>> >
>>> > // Create a stack-allocated handle scope.
>>> > v8::HandleScope handle_scope(instance->isolate);
>>> >
>>> > // Create a new context.
>>> > v8::Local<v8::Context> context =
>>> v8::Context::New(instance->isolate);
>>> >
>>> > // Enter the context for compiling and running the hello world
>>> script.
>>> > v8::Context::Scope context_scope(context);
>>> >
>>> > {
>>> >
>>> > // Create a string containing the JavaScript source code.
>>> > v8::Local<v8::String> source =
>>> > v8::String::NewFromUtf8(instance->isolate, jscript,
>>> > 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->isolate, result);
>>> > printf("%s\n", *utf8);
>>> > }
>>> > }
>>> > }
>>> >
>>> > Main File
>>> > int main(int argc, char **argv)
>>> > {
>>> > char *script;
>>> > void *instance;
>>> >
>>> > instance = mjse_create_instance(argv);
>>> >
>>> > script = "function js_add_elements(var1, var2) \
>>> > { \
>>> > var var3 = parseInt(var1) + parseInt(var2); \
>>> > var result = 'Addition of ' + var1 + ' and ' +
>>> var2 + ' results ' + var3; \
>>> > return result; \
>>> > };";
>>> > mjse_execute_script(instance, script);
>>> >
>>> > script = "js_add_elements(2, 3);";
>>> > mjse_execute_script(instance, script);
>>> >
>>> > mjse_destroy_instance(instance);
>>> > return 0;
>>> > }
>>> >
>>> > Now whats happening, while executing javascript first time it executes
>>> fine. But while trying to execute second time (letter in red), it gets
>>> exception.
>>> >
>>> > I understand, it is creating new v8 Local context each time, and does
>>> not have js1.js details, hence getting exception. I also found in web we
>>> can have v8 Global context and refer the context while executing for second
>>> time.
>>> >
>>> > However I have not been able to find, how to declare v8 global context
>>> and store / move v8 local context there and refer it during second time
>>> execution. Please let me know with a sample/example code.
>>> >
>>> > Thanks
>>> > Austin
>>>
>>> You can make the context persistent like this:
>>>
>>> if (instance->context == nullptr) {
>>> v8::Local<v8::Context> context = v8::Context::New(instance->isolate);
>>> instance->context = new v8::Global<v8::Context>(instance->isolate,
>>> context);
>>> }
>>>
>>> v8::Local<v8::Context> context(instance->isolate, instance->context);
>>> v8::Context::Scope context_scope(context);
>>>
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