JS_NewContext 中的 JSAPI 段错误
JSAPI segfault in JS_NewContext
我正在编写一个嵌入 SpiderMonkey 的简单 C++ 程序。不幸的是，它在 JS_NewContext().
中出现段错误
程序（另存为jsapi_use.cpp）：
#define __STDC_LIMIT_MACROS
#include <js/Initialization.h>
#include <jsapi.h>
#include <stdint.h>
static JSClass global_class = {
#if 0
.name = "global",
.flags = JSCLASS_GLOBAL_FLAGS,
.addProperty = nullptr,
.delProperty = nullptr,
.getProperty = nullptr,
.setProperty = nullptr,
.enumerate = nullptr,
.resolve = nullptr,
.mayResolve = nullptr,
.finalize = nullptr,
.call = nullptr,
.hasInstance = nullptr,
.construct = nullptr,
.trace = JS_GlobalObjectTraceHook,
#else
"global", JSCLASS_GLOBAL_FLAGS,
nullptr, nullptr,
nullptr, nullptr,
nullptr, nullptr,
nullptr, nullptr,
nullptr, nullptr,
nullptr, JS_GlobalObjectTraceHook,
{0},
#endif
};
int main() {
if (!JS_Init())
return 1;
JSRuntime *rt =
JS_NewRuntime(8L * 1024 * 1024 /*, JS::DefaultHeapMaxBytes, nullptr*/);
if (nullptr == rt)
return 1;
JSContext *cx = JS_NewContext(rt, 8192);
if (!cx) {
return 1;
}
{
JSAutoRequest ar(cx);
JS::RootedObject global(cx, JS_NewGlobalObject(cx, &global_class, nullptr,
JS::FireOnNewGlobalHook));
if (!global)
return 1;
JS::RootedValue rval(cx);
{
JSAutoCompartment ac(cx, global);
JS_InitStandardClasses(cx, global);
const char *script = "'hello'+'world, it is '+new Date();";
const char *filename = "noname";
auto lineno = 1U;
JS::CompileOptions opts(cx);
opts.setFileAndLine(filename, lineno);
bool ok = JS::Evaluate(cx, opts, script, strlen(script), &rval);
if (!ok)
return 1;
}
if (rval.isString()) {
JSString *string = rval.toString();
puts(JS_EncodeString(cx, string));
}
}
JS_DestroyContext(cx);
JS_DestroyRuntime(rt);
JS_ShutDown();
return 0;
}
它在 JS_NewContext 崩溃。
我的生成文件：
MAKEFLAGS := -r -R
CXX := g++
CXXFLAGS += -g3 -std=gnu++14
TARGET = $(subst ','\'',$@)#')
SOURCE = $(subst ','\'',$<)#')
PKG_CFLAGS=$(shell pkg-config --cflags mozjs-45)
PKG_LDFLAGS=$(shell pkg-config --libs mozjs-45)
%.o: %.cpp Makefile
$(CXX) $(CPPFLAGS) -c -o $(TARGET) $(CXXFLAGS) $(PKG_CFLAGS) $(SOURCE)
%: %.o
$(CXX) -o $(TARGET) $(SOURCE) $(PKG_LDFLAGS) -lz -lpthread -ldl
%.iii: %.cpp Makefile
cpp $(CPPFLAGS) -dD -CC -o $(TARGET) $(PKG_CFLAGS) $(SOURCE)
clang-format -i -- $(TARGET)
运行 make jsapi_use; ./jsapi_use 导致 Segmentation fault (core dumped).gdb` 显示该程序由于取消引用 NULL 指针而在 SpiderMonkey 内部发生段错误。
我在 Fedora 24 Linux.
上使用来自 mozjs45 的 SpiderMonkey
GDB 回溯
Thread 1 "jsapi_use" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
#0 0x0000000000000000 in ?? ()
#1 0x00007ffff7a6adb5 in js::ScriptBytecodeHasher::hash (l=<synthetic pointer>, l=<synthetic pointer>) at /usr/src/debug/firefox-45.4.0esr/js/src/jsscript.h:2412
#2 js::detail::HashTable<js::SharedScriptData* const, js::HashSet<js::SharedScriptData*, js::ScriptBytecodeHasher, js::SystemAllocPolicy>::SetOps, js::SystemAllocPolicy>::prepareHash (l=<synthetic pointer>) at ../../dist/include/js/HashTable.h:1126
#3 js::detail::HashTable<js::SharedScriptData* const, js::HashSet<js::SharedScriptData*, js::ScriptBytecodeHasher, js::SystemAllocPolicy>::SetOps, js::SystemAllocPolicy>::lookupForAdd (l=<synthetic pointer>, this=<optimized out>) at ../../dist/include/js/HashTable.h:1638
#4 js::HashSet<js::SharedScriptData*, js::ScriptBytecodeHasher, js::SystemAllocPolicy>::lookupForAdd (l=<synthetic pointer>, this=<optimized out>) at ../../dist/include/js/HashTable.h:386
#5 SaveSharedScriptData (cx=cx@entry=0x639ed0, script=..., ssd=<optimized out>, nsrcnotes=1) at /usr/src/debug/firefox-45.4.0esr/js/src/jsscript.cpp:2502
#6 0x00007ffff7a6b2f7 in JSScript::fullyInitTrivial (cx=cx@entry=0x639ed0, script=..., script@entry=...) at /usr/src/debug/firefox-45.4.0esr/js/src/jsscript.cpp:2886
#7 0x00007ffff7a2a451 in CreateFunctionPrototype(JSContext *, enum JSProtoKey) (cx=0x639ed0, key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/jsfun.cpp:785
#8 0x00007ffff7ae37b3 in js::GlobalObject::resolveConstructor (cx=0x639ed0, global=..., key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:158
#9 0x00007ffff7ae3da7 in js::GlobalObject::ensureConstructor (cx=cx@entry=0x639ed0, global=..., global@entry=..., key=key@entry=JSProto_Function) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:98
#10 0x00007ffff79677ed in CreateObjectConstructor(JSContext *, enum JSProtoKey) (cx=0x639ed0, key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/builtin/Object.cpp:1035
#11 0x00007ffff7ae382f in js::GlobalObject::resolveConstructor (cx=0x639ed0, global=..., key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:166
#12 0x00007ffff772dda6 in CreateArrayPrototype(JSContext *, enum JSProtoKey) (cx=0x639ed0, key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.h:342
#13 0x00007ffff7ae18ce in InitBareBuiltinCtor(JSContext *, JS::Handle<js::GlobalObject*>, enum JSProtoKey) (cx=cx@entry=0x639ed0, global=..., global@entry=..., protoKey=protoKey@entry=JSProto_Array) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:368
#14 0x00007ffff7ae1b08 in js::GlobalObject::initSelfHostingBuiltins (cx=cx@entry=0x639ed0, global=global@entry=..., builtins=builtins@entry=0x7ffff7dbefa0 <intrinsic_functions>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:413
#15 0x00007ffff7b5041f in JSRuntime::createSelfHostingGlobal (cx=cx@entry=0x639ed0) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/SelfHosting.cpp:1730
#16 0x00007ffff7b5056f in JSRuntime::initSelfHosting (this=0x617850, cx=0x639ed0) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/SelfHosting.cpp:1754
#17 0x00007ffff79e2103 in js::NewContext (rt=rt@entry=0x617850, stackChunkSize=stackChunkSize@entry=8192) at /usr/src/debug/firefox-45.4.0esr/js/src/jscntxt.cpp:122
#18 0x00007ffff79e21ba in JS_NewContext (rt=rt@entry=0x617850, stackChunkSize=stackChunkSize@entry=8192) at /usr/src/debug/firefox-45.4.0esr/js/src/jsapi.cpp:566
#19 0x0000000000400e4f in main () at jsapi_use.cpp:41
问题是由Spidermonkey 库中未定义的符号引起的。即，HashBytes() 函数未在 libmozjs-45.so 中定义。此函数由调试回溯中显示的 js::ScriptBytecodeHasher::hash() 函数调用。
如果列出库符号，您会发现 HashBytes 只是 "weakly defined"。
$nm -gC libmozjs-45.so | grep HashBytes
w mozilla::HashBytes(void const*, unsigned long)
"w"该符号是一个弱符号，没有被明确标记为弱对象符号。
要解决此问题，您需要 link mfbt 库到 libmozjs-45.so。
您可以通过更改 js/src/moz.build 文件并重建 Spidermonkey 来做到这一点。
在moz.build中替换
if not CONFIG['JS_STANDALONE']:
和
if CONFIG['JS_STANDALONE']:
DEFINES['IMPL_MFBT'] = True
USE_LIBS += [
'mfbt',
]
else:
您将获得：
if CONFIG['JS_STANDALONE']:
DEFINES['IMPL_MFBT'] = True
USE_LIBS += [
'mfbt',
]
else:
CONFIGURE_SUBST_FILES += [
'../../config/autoconf-js.mk',
'../../config/emptyvars-js.mk',
]
重建后你将拥有：
$nm -gC libmozjs-45.so | grep HashBytes
0000000000b66e07 T mozilla::HashBytes(void const*, unsigned long)
我正在编写一个嵌入 SpiderMonkey 的简单 C++ 程序。不幸的是，它在 JS_NewContext().
程序（另存为jsapi_use.cpp）：
#define __STDC_LIMIT_MACROS
#include <js/Initialization.h>
#include <jsapi.h>
#include <stdint.h>
static JSClass global_class = {
#if 0
.name = "global",
.flags = JSCLASS_GLOBAL_FLAGS,
.addProperty = nullptr,
.delProperty = nullptr,
.getProperty = nullptr,
.setProperty = nullptr,
.enumerate = nullptr,
.resolve = nullptr,
.mayResolve = nullptr,
.finalize = nullptr,
.call = nullptr,
.hasInstance = nullptr,
.construct = nullptr,
.trace = JS_GlobalObjectTraceHook,
#else
"global", JSCLASS_GLOBAL_FLAGS,
nullptr, nullptr,
nullptr, nullptr,
nullptr, nullptr,
nullptr, nullptr,
nullptr, nullptr,
nullptr, JS_GlobalObjectTraceHook,
{0},
#endif
};
int main() {
if (!JS_Init())
return 1;
JSRuntime *rt =
JS_NewRuntime(8L * 1024 * 1024 /*, JS::DefaultHeapMaxBytes, nullptr*/);
if (nullptr == rt)
return 1;
JSContext *cx = JS_NewContext(rt, 8192);
if (!cx) {
return 1;
}
{
JSAutoRequest ar(cx);
JS::RootedObject global(cx, JS_NewGlobalObject(cx, &global_class, nullptr,
JS::FireOnNewGlobalHook));
if (!global)
return 1;
JS::RootedValue rval(cx);
{
JSAutoCompartment ac(cx, global);
JS_InitStandardClasses(cx, global);
const char *script = "'hello'+'world, it is '+new Date();";
const char *filename = "noname";
auto lineno = 1U;
JS::CompileOptions opts(cx);
opts.setFileAndLine(filename, lineno);
bool ok = JS::Evaluate(cx, opts, script, strlen(script), &rval);
if (!ok)
return 1;
}
if (rval.isString()) {
JSString *string = rval.toString();
puts(JS_EncodeString(cx, string));
}
}
JS_DestroyContext(cx);
JS_DestroyRuntime(rt);
JS_ShutDown();
return 0;
}
它在 JS_NewContext 崩溃。
我的生成文件： MAKEFLAGS := -r -R
CXX := g++
CXXFLAGS += -g3 -std=gnu++14
TARGET = $(subst ','\'',$@)#')
SOURCE = $(subst ','\'',$<)#')
PKG_CFLAGS=$(shell pkg-config --cflags mozjs-45)
PKG_LDFLAGS=$(shell pkg-config --libs mozjs-45)
%.o: %.cpp Makefile
$(CXX) $(CPPFLAGS) -c -o $(TARGET) $(CXXFLAGS) $(PKG_CFLAGS) $(SOURCE)
%: %.o
$(CXX) -o $(TARGET) $(SOURCE) $(PKG_LDFLAGS) -lz -lpthread -ldl
%.iii: %.cpp Makefile
cpp $(CPPFLAGS) -dD -CC -o $(TARGET) $(PKG_CFLAGS) $(SOURCE)
clang-format -i -- $(TARGET)
运行 make jsapi_use; ./jsapi_use 导致 Segmentation fault (core dumped).gdb` 显示该程序由于取消引用 NULL 指针而在 SpiderMonkey 内部发生段错误。
我在 Fedora 24 Linux.
上使用来自mozjs45 的 SpiderMonkey
GDB 回溯
Thread 1 "jsapi_use" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
#0 0x0000000000000000 in ?? ()
#1 0x00007ffff7a6adb5 in js::ScriptBytecodeHasher::hash (l=<synthetic pointer>, l=<synthetic pointer>) at /usr/src/debug/firefox-45.4.0esr/js/src/jsscript.h:2412
#2 js::detail::HashTable<js::SharedScriptData* const, js::HashSet<js::SharedScriptData*, js::ScriptBytecodeHasher, js::SystemAllocPolicy>::SetOps, js::SystemAllocPolicy>::prepareHash (l=<synthetic pointer>) at ../../dist/include/js/HashTable.h:1126
#3 js::detail::HashTable<js::SharedScriptData* const, js::HashSet<js::SharedScriptData*, js::ScriptBytecodeHasher, js::SystemAllocPolicy>::SetOps, js::SystemAllocPolicy>::lookupForAdd (l=<synthetic pointer>, this=<optimized out>) at ../../dist/include/js/HashTable.h:1638
#4 js::HashSet<js::SharedScriptData*, js::ScriptBytecodeHasher, js::SystemAllocPolicy>::lookupForAdd (l=<synthetic pointer>, this=<optimized out>) at ../../dist/include/js/HashTable.h:386
#5 SaveSharedScriptData (cx=cx@entry=0x639ed0, script=..., ssd=<optimized out>, nsrcnotes=1) at /usr/src/debug/firefox-45.4.0esr/js/src/jsscript.cpp:2502
#6 0x00007ffff7a6b2f7 in JSScript::fullyInitTrivial (cx=cx@entry=0x639ed0, script=..., script@entry=...) at /usr/src/debug/firefox-45.4.0esr/js/src/jsscript.cpp:2886
#7 0x00007ffff7a2a451 in CreateFunctionPrototype(JSContext *, enum JSProtoKey) (cx=0x639ed0, key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/jsfun.cpp:785
#8 0x00007ffff7ae37b3 in js::GlobalObject::resolveConstructor (cx=0x639ed0, global=..., key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:158
#9 0x00007ffff7ae3da7 in js::GlobalObject::ensureConstructor (cx=cx@entry=0x639ed0, global=..., global@entry=..., key=key@entry=JSProto_Function) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:98
#10 0x00007ffff79677ed in CreateObjectConstructor(JSContext *, enum JSProtoKey) (cx=0x639ed0, key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/builtin/Object.cpp:1035
#11 0x00007ffff7ae382f in js::GlobalObject::resolveConstructor (cx=0x639ed0, global=..., key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:166
#12 0x00007ffff772dda6 in CreateArrayPrototype(JSContext *, enum JSProtoKey) (cx=0x639ed0, key=<optimized out>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.h:342
#13 0x00007ffff7ae18ce in InitBareBuiltinCtor(JSContext *, JS::Handle<js::GlobalObject*>, enum JSProtoKey) (cx=cx@entry=0x639ed0, global=..., global@entry=..., protoKey=protoKey@entry=JSProto_Array) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:368
#14 0x00007ffff7ae1b08 in js::GlobalObject::initSelfHostingBuiltins (cx=cx@entry=0x639ed0, global=global@entry=..., builtins=builtins@entry=0x7ffff7dbefa0 <intrinsic_functions>) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/GlobalObject.cpp:413
#15 0x00007ffff7b5041f in JSRuntime::createSelfHostingGlobal (cx=cx@entry=0x639ed0) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/SelfHosting.cpp:1730
#16 0x00007ffff7b5056f in JSRuntime::initSelfHosting (this=0x617850, cx=0x639ed0) at /usr/src/debug/firefox-45.4.0esr/js/src/vm/SelfHosting.cpp:1754
#17 0x00007ffff79e2103 in js::NewContext (rt=rt@entry=0x617850, stackChunkSize=stackChunkSize@entry=8192) at /usr/src/debug/firefox-45.4.0esr/js/src/jscntxt.cpp:122
#18 0x00007ffff79e21ba in JS_NewContext (rt=rt@entry=0x617850, stackChunkSize=stackChunkSize@entry=8192) at /usr/src/debug/firefox-45.4.0esr/js/src/jsapi.cpp:566
#19 0x0000000000400e4f in main () at jsapi_use.cpp:41
问题是由Spidermonkey 库中未定义的符号引起的。即，HashBytes() 函数未在 libmozjs-45.so 中定义。此函数由调试回溯中显示的 js::ScriptBytecodeHasher::hash() 函数调用。
如果列出库符号，您会发现 HashBytes 只是 "weakly defined"。
$nm -gC libmozjs-45.so | grep HashBytes
w mozilla::HashBytes(void const*, unsigned long)
"w"该符号是一个弱符号，没有被明确标记为弱对象符号。
要解决此问题，您需要 link mfbt 库到 libmozjs-45.so。
您可以通过更改 js/src/moz.build 文件并重建 Spidermonkey 来做到这一点。
在moz.build中替换
if not CONFIG['JS_STANDALONE']:
和
if CONFIG['JS_STANDALONE']:
DEFINES['IMPL_MFBT'] = True
USE_LIBS += [
'mfbt',
]
else:
您将获得：
if CONFIG['JS_STANDALONE']:
DEFINES['IMPL_MFBT'] = True
USE_LIBS += [
'mfbt',
]
else:
CONFIGURE_SUBST_FILES += [
'../../config/autoconf-js.mk',
'../../config/emptyvars-js.mk',
]
重建后你将拥有：
$nm -gC libmozjs-45.so | grep HashBytes
0000000000b66e07 T mozilla::HashBytes(void const*, unsigned long)