https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82562
Bug ID: 82562
Summary: Incorrect warning: use copy-assignment or
copy-initialization instead when copying build
objects.
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: andi at mozilla dot com
Target Milestone: ---
Trying to build firefox with gcc8 I get this error, when building with treat
-Werror:
/usr/bin/g++-8 -std=gnu++11 -o RegExp.o -c
-I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/system_wrappers -include
/root/firefox-gcc-last/config/gcc_hidden.h -DDEBUG=1 -DENABLE_BINARYDATA
-DENABLE_SIMD -DENABLE_WASM_THREAD_OPS -DWASM_HUGE_MEMORY -DJS_CACHEIR_SPEW
-DENABLE_SHARED_ARRAY_BUFFER -DEXPORT_JS_API -DJS_HAS_CTYPES
'-DDLL_PREFIX="lib"' '-DDLL_SUFFIX=".so"' -DFFI_BUILDING -DMOZ_HAS_MOZGLUE
-I/root/firefox-gcc-last/js/src
-I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/js/src
-I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/js/src/ctypes/libffi/include
-I/root/firefox-gcc-last/js/src/ctypes/libffi/src/x86
-I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/include
-I/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/dist/include/nspr -fPIC
-DMOZILLA_CLIENT -include
/root/firefox-gcc-last/obj-x86_64-pc-linux-gnu/js/src/js-confdefs.h -MD -MP -MF
.deps/RegExp.o.pp -Wall -Wc++11-compat -Wempty-body -Wignored-qualifiers
-Woverloaded-virtual -Wpointer-arith -Wsign-compare -Wtype-limits
-Wunreachable-code -Wwrite-strings -Wno-invalid-offsetof -Wc++14-compat
-Wc++1z-compat -Wduplicated-cond -Wimplicit-fallthrough
-Wno-error=maybe-uninitialized -Wno-error=deprecated-declarations
-Wno-error=array-bounds -Wno-error=free-nonheap-object -Wformat
-Wformat-overflow=2 -Wno-noexcept-type -fno-rtti -fno-exceptions
-fno-math-errno -pthread -pipe -g -freorder-blocks -O3 -fno-omit-frame-pointer
-Werror -Wno-shadow -Werror=format -fno-strict-aliasing
/root/firefox-gcc-last/js/src/builtin/RegExp.cpp
In file included from /root/firefox-gcc-last/js/src/builtin/RegExp.cpp:24:0:
/root/firefox-gcc-last/js/src/vm/NativeObject-inl.h: In member function 'void
js::NativeObject::copyDenseElements(uint32_t, const JS::Value*, uint32_t)':
/root/firefox-gcc-last/js/src/vm/NativeObject-inl.h:155:67: error: 'void*
memcpy(void*, const void*, size_t)' writing to an object of non-trivially
copyable type 'class js::HeapSlot'; use copy-assignment or copy-initialization
instead [-Werror=class-memaccess]
memcpy(&elements_[dstStart], src, count * sizeof(HeapSlot));
^
In file included from /root/firefox-gcc-last/js/src/jsatom.h:15:0,
from /root/firefox-gcc-last/js/src/vm/Runtime.h:22,
from /root/firefox-gcc-last/js/src/jscntxt.h:21,
from /root/firefox-gcc-last/js/src/vm/RegExpObject.h:15,
from /root/firefox-gcc-last/js/src/builtin/RegExp.h:10,
from /root/firefox-gcc-last/js/src/builtin/RegExp.cpp:7:
/root/firefox-gcc-last/js/src/gc/Barrier.h:655:7: note: 'class js::HeapSlot'
declared here
class HeapSlot : public WriteBarrieredBase<Value>
^~~~~~~~
In file included from /root/firefox-gcc-last/js/src/builtin/RegExp.cpp:24:0:
/root/firefox-gcc-last/js/src/vm/NativeObject-inl.h: In member function 'void
js::NativeObject::initDenseElements(const JS::Value*, uint32_t)':
/root/firefox-gcc-last/js/src/vm/NativeObject-inl.h:184:52: error: 'void*
memcpy(void*, const void*, size_t)' writing to an object of non-trivially
copyable type 'class js::HeapSlot'; use copy-assignment or copy-initialization
instead [-Werror=class-memaccess]
memcpy(elements_, src, count * sizeof(HeapSlot));
I don't think that the warning is valid since what we try to do is copy in
eleements_ the number of 'count' elements of type HeadSlop from src.
