Warnings generated despite -isystem - c++

We are using two frameworks, Beast and Boost, when compiling one of our applications. In some Boost code used by Beast, a warning is generated by g++, because it thinks there is a possible uninitialized variable. However, we include boost and beast using the "-isystem" flag. This should stop the warning from being shown, but it isn't. Any ideas why?
Below you can see the compilation command and its output, with some anonymization.
/home/user/code/thirdparty/supplier/6.0/sysroots/x86_64-suppliersdk-linux/usr/bin/arm-supplier-linux-gnueabi/arm-supplier-linux-gnueabi-g++ --sysroot=/home/user/code/thirdparty/supplier/6.0/sysroots/armv7a-neon-supplier-linux-gnueabi -DBOOST_ASIO_DISABLE_EPOLL=1 -DEIGEN_MPL2_ONLY -DUSE_LOG -DLOG_THROUGH_SERVERSERVICE=1 -DARM -DNDEBUG -DAPP_TYPE_IS_PT -DOSIRIS_RELEASE_NUMBER=\"0.0\" -DLOGCONFIGFILE=\"app1_dev.log4\" -DCONFIGFILE=\"app1_native.cfg\" -DCONFIGFILE=\"app1_native.cfg\" -DLOGCONFIGFILE=\"app1_dev.log4\" -pthread -std=c++11 -mcpu=cortex-a8 -mfpu=neon -mfloat-abi=softfp -O2 -ftree-vectorize -ffast-math -Wall -Wextra -Wno-unused-parameter -Wcast-align -Wuninitialized -Wmissing-include-dirs -Wpedantic -I binaryprotocol/include -I common/include -I config/include -I connectivity/include -I core/include -I socketserver/include -isystem /home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include -isystem /home/user/code/thirdparty/log4cplus/1.2.0/arm/b993705d/include -isystem /home/user/code/thirdparty/openssl/1.0.2j/arm/b993705d/include -isystem ../external/common/modernjson -isystem ../external/common/pstreams -isystem ../external/common/beast/include -MD -MF ../osiris-obj/arm/b993705d/mains/app1/TLSWSClient.d -c mains/app1/TLSWSClient.cpp -o ../osiris-obj/arm/b993705d/mains/app1/TLSWSClient.o
In copy constructor ~boost::asio::detail::consuming_buffers<Buffer, Buffers>::consuming_buffers(const boost::asio::detail::consuming_buffers<Buffer, Buffers>&) [with Buffer = boost::asio::const_buffer; Buffers = beast::detail::buffer_cat_helper<beast::http::detail::chunk_encode_delim, boost::asio::null_buffers, boost::asio::const_buffers_1>]~:
cc1plus: warning: ~*((void*)& second +8)~ may be used uninitialized in this function [-Wmaybe-uninitialized]
In file included from /home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include/boost/asio/impl/write.hpp:23:0,
from /home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include/boost/asio/write.hpp:618,
from /home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include/boost/asio/buffered_write_stream.hpp:29,
from /home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include/boost/asio/buffered_stream.hpp:22,
from /home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include/boost/asio.hpp:38,
from ../external/common/beast/include/beast/websocket/stream.hpp:18,
from ../external/common/beast/include/beast/websocket.hpp:14,
from mains/app1/TLSWSClient.h:13,
from mains/app1/TLSWSClient.cpp:11:
/home/user/code/thirdparty/boost/1.64.0/arm/b993705d/include/boost/asio/detail/consuming_buffers.hpp:191:38: note: ~*((void*)& second +8)~ was declared here
typename Buffers::const_iterator second = other.begin_remainder_;
Running Ubuntu 16.04. g++ provided by a supplier, its version below.
/home/user/code/thirdparty/supplier/6.0/sysroots/x86_64-suppliersdk-linux/usr/bin/arm-supplier-linux-gnueabi/arm-supplier-linux-gnueabi-g++ --version
arm-supplier-linux-gnueabi-g++ (GCC) 5.3.0

"-i" doesn't always prevent all warnings. There was a period of time where gcc produced false positives for "maybe uninitialized." This looks just like one of those times.

Related

compile simple github fails at ext submodule

i am trying to compile this git https://github.com/yapb/yapb locally
i am using ubuntu 64bit, and it says i must compile 32bit
i am using now
CC=clang CXX=clang meson build-clang
but get this error
FAILED: yapb.so.p/src_chatlib.cpp.o
clang -Iyapb.so.p -I. -I.. -fvisibility=hidden -flto
-fcolor-diagnostics -DNDEBUG -D_FILE_OFFSET_BITS=64 -Wall
-Winvalid-pch -Wnon-virtual-dtor -Wextra -Wpedantic -Werror -std=c++14
-fno-exceptions -O3 -DVERSION_GENERATED -fno-threadsafe-statics
-fno-exceptions -fno-rtti -m32 -pedantic -fdata-sections
-ffunction-sections -mtune=generic -fno-builtin -funroll-loops
-fomit-frame-pointer -fno-stack-protector -fvisibility=hidden
-fvisibility-inlines-hidden -msse2 -mfpmath=sse -fPIC
-isystem../ext/crlib -isystem../ext -isystem../inc -isystem..
-isystem. -MD -MQ yapb.so.p/src_chatlib.cpp.o -MF
yapb.so.p/src_chatlib.cpp.o.d -o yapb.so.p/src_chatlib.cpp.o -c
../src/chatlib.cpp
In file included from ../src/chatlib.cpp:8:
In file included from ../inc/yapb.h:10:
In file included from ../ext/hlsdk/extdll.h:28:
In file included from ../ext/crlib/crlib/string.h:17:
../ext/crlib/crlib/array.h:15:10: fatal error: 'initializer_list' file not found
#include <initializer_list>```
Double-check the pre-requisites mentioned in YaPB Building the Bot page.
Try and open a regular CMD (instead of Powershell), making sure it inherits all your previous setups (meaning its %PATH% does reference g++.exe, pip.exe, and so on.

How to use linked libraries compiled with libc++ libstdc++ mixed

I am trying to write a script that uses a library compiled with clang and another library compiled with G++, I get the following error:
ld.lld: error: undefined symbol: myFunction()
Which (according to this Difference between string and char[] types in C++) is apparently due to std::string meaning different things in different versions of G++ and clang.
Does this mean I have to rewrite the Makefile of my target library to use the same version of G++/Clang? Because that seems like an awful amount of effort just to link a prewritten library, and I think I must be missing something here.
More info
I am compiling v8_shell using ninja -C out/debug
defines = -DUSE_UDEV -DUSE_AURA=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1 -DUSE_X11=1 -DNO_TCMALLOC -DMEMORY_TOOL_REPLACES_ALLOCATOR -DMEMORY_SANITIZER_INITIAL_SIZE -DADDRESS_SANITIZER -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_GNU_SOURCE -DCR_CLANG_REVISION=\"353250-1\" -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DCOMPONENT_BUILD -D_LIBCPP_ABI_UNSTABLE -D_LIBCPP_ABI_VERSION=Cr -DCR_LIBCXX_REVISION=349080 -DCR_LIBCXXABI_REVISION=347903 -D_LIBCPP_ENABLE_NODISCARD -DCR_SYSROOT_HASH=e7c53f04bd88d29d075bfd1f62b073aeb69cbe09 -D_DEBUG -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DWTF_USE_DYNAMIC_ANNOTATIONS=1 -DENABLE_DISASSEMBLER -DV8_TYPED_ARRAY_MAX_SIZE_IN_HEAP=64 -DENABLE_GDB_JIT_INTERFACE -DENABLE_MINOR_MC -DOBJECT_PRINT -DVERIFY_HEAP -DV8_TRACE_MAPS -DV8_ENABLE_ALLOCATION_TIMEOUT -DV8_ENABLE_FORCE_SLOW_PATH -DV8_INTL_SUPPORT -DENABLE_HANDLE_ZAPPING -DV8_USE_SNAPSHOT -DV8_USE_EXTERNAL_STARTUP_DATA -DV8_CONCURRENT_MARKING -DV8_CHECK_MICROTASKS_SCOPES_CONSISTENCY -DV8_EMBEDDED_BUILTINS -DV8_ENABLE_CHECKS -DV8_DEPRECATION_WARNINGS -DV8_IMMINENT_DEPRECATION_WARNINGS -DV8_TARGET_ARCH_X64 -DDEBUG -DDISABLE_UNTRUSTED_CODE_MITIGATIONS -DUSING_V8_SHARED -DV8_ENABLE_CHECKS -DV8_DEPRECATION_WARNINGS -DV8_IMMINENT_DEPRECATION_WARNINGS -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DUSE_CHROMIUM_ICU=1 -DICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_FILE -DUCHAR_TYPE=uint16_t -DUSING_V8_BASE_SHARED -DUSING_V8_PLATFORM_SHARED
include_dirs = -I../.. -Igen -I../.. -Igen -I../../include -Igen/include -I../../third_party/icu/source/common -I../../third_party/icu/source/i18n -I../../include
cflags = -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -funwind-tables -fPIC -B../../third_party/binutils/Linux_x64/Release/bin -pthread -fcolor-diagnostics -fmerge-all-constants -Xclang -mllvm -Xclang -instcombine-lower-dbg-declare=0 -no-canonical-prefixes -fcomplete-member-pointers -m64 -march=x86-64 -Wall -Werror -Wextra -Wimplicit-fallthrough -Wthread-safety -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -Wno-ignored-pragma-optimize -fno-omit-frame-pointer -g2 -gsplit-dwarf -ggnu-pubnames -gcolumn-info -fsanitize=address -fsanitize-address-use-after-scope -fsanitize-blacklist=../../tools/memory/asan/blacklist.txt -fvisibility=hidden -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wmissing-field-initializers -Wextra-semi -Winconsistent-missing-override -Wunreachable-code -Wshorten-64-to-32 -O2 -fno-ident -fdata-sections -ffunction-sections
cflags_cc = -Wno-undefined-bool-conversion -Wno-tautological-undefined-compare -std=c++14 -fno-exceptions -fno-rtti -nostdinc++ -isystem../../buildtools/third_party/libc++/trunk/include -isystem../../buildtools/third_party/libc++abi/trunk/include --sysroot=../../build/linux/debian_sid_amd64-sysroot -fvisibility-inlines-hidden
label_name = v8_shell
target_out_dir = obj
target_output_name = v8_shell
build obj/v8_shell/shell.o: cxx ../../samples/shell.cc || obj/generate_bytecode_builtins_list.stamp obj/run_torque.stamp obj/v8_dump_build_config.stamp obj/src/inspector/protocol_generated_sources.stamp obj/third_party/icu/icudata.stamp
build ./v8_shell: link obj/v8_shell/shell.o obj/build/config/sanitizers/liboptions_sources.a | ./libv8.so.TOC ./libv8_libbase.so.TOC ./libv8_libplatform.so.TOC ./libicui18n.so.TOC ./libicuuc.so.TOC ./libc++.so.TOC || obj/build/win/default_exe_manifest.stamp obj/v8_dump_build_config.stamp obj/build/config/executable_deps.stamp
ldflags = -pie -Wl,--fatal-warnings -fPIC -Wl,-z,noexecstack -Wl,-z,relro -fuse-ld=lld -Wl,--color-diagnostics -m64 -Werror -Wl,--gdb-index -rdynamic -nostdlib++ --sysroot=../../build/linux/debian_sid_amd64-sysroot -L../../build/linux/debian_sid_amd64-sysroot/usr/local/lib/x86_64-linux-gnu -Wl,-rpath-link=../../build/linux/debian_sid_amd64-sysroot/usr/local/lib/x86_64-linux-gnu -L../../build/linux/debian_sid_amd64-sysroot/lib/x86_64-linux-gnu -Wl,-rpath-link=../../build/linux/debian_sid_amd64-sysroot/lib/x86_64-linux-gnu -L../../build/linux/debian_sid_amd64-sysroot/usr/lib/x86_64-linux-gnu -Wl,-rpath-link=../../build/linux/debian_sid_amd64-sysroot/usr/lib/x86_64-linux-gnu -fsanitize=address -fsanitize-address-use-after-scope -pie -Wl,-rpath-link=. -Wl,--disable-new-dtags -Wl,-rpath=\$$ORIGIN/. -Wl,-rpath-link=. -Wl,-O2 -Wl,--gc-sections -Wl,-u_sanitizer_options_link_helper -fsanitize=address -fsanitize-address-use-after-scope
libs = -L . -ldl -lpthread -lrt
output_extension =
output_dir = .
solibs = ./libtester.so ./libv8.so ./libv8_libbase.so ./libv8_libplatform.so ./libicui18n.so ./libicuuc.so ./libc++.so
Link to code is here:
https://github.com/v8/v8/blob/master/samples/shell.cc
All I have done is add a test library that returns a std::string and this is called from shell.cc.
This test library is compiled with
clang++ -shared -o libtester tester.cpp -fPIC -L . -lpthread
Which yields undefined symbol errors.
I can get it to compile by forcing libc++ that v8 seems to use, but then I get a whole host of core dumps and other errors at runtime, so I don't think thats a legitimate fix.
clang++ -shared -o libtester.so tester.cpp -fPIC -std=c++11 -L . -stdlib=libc++ -lpthread
Example code snippet:
tester.cpp
std::string myFunction() {
std::string newstring;
// do something
return newstring;
}
shell.cc
std::string test = myFunction();
cout << test;
Update please see these posts that document it further C++ Undefined symbol related to std::string in static lib
Can't link libFuzzer.a using clang with libc++
Theres no real answer apart from use libstdc++ rather than libc++ for everything, but thats not really an option to convert an entire project like v8 to libstdc++
The build recipe you use for V8 builds it with -D_LIBCPP_ABI_UNSTABLE -D_LIBCPP_ABI_VERSION=Cr -DCR_LIBCXX_REVISION=349080 -DCR_LIBCXXABI_REVISION=347903. According to libc++ ABI stability, these macros affect the library ABI. Your separate compilation uses just -stdlib=libc++, so it does not enable the incompatible ABI.
You might get better results if you use a different recipe for building V8, something that uses the system C++ standard library with its default (stable) ABI.
This is the solution for compiling v8 with libstdc++.
Type the following command
gn args out/stdc
Add the following arguments to the args file:
is_clang = true
use_custom_libcxx_for_host=false
use_custom_libcxx=false
libcxx_abi_unstable=false
Build with
ninja -C out/stdc

Code base not finding standard C++ library header

I am compiling an example application from the SDK repository of a third party vendor. I receive an error that one of the C++ header's (algorithm) cannot be found:
if [ ! -d .deps/ ]; then mkdir -p .deps/; fi
/opt/llvm-3.8.0/bin/clang++ -M -isystem/opt/tbricks/sdk/include64 -I../../.. -I../../../.. -I./../../../.. -DLINUX -DLINUX64 -DTB_USE_RCU -DURCU_INLINE_SMALL_FUNCTIONS -DU_USING_ICU_NAMESPACE=0 -DNDEBUG -D_POSIX_PTHREAD_SEMANTICS -fPIC -D_GNU_SOURCE -DTB_USE_RCU -DTB_USE_RCU -D_GLIBCXX_USE_CXX11_ABI=0 -m64 --gcc-toolchain=/opt/gcc-5.2.0 -flto=full -std=gnu++14 -D_GLIBCXX_DEPRECATED= -pipe -fno-omit-frame-pointer -ffast-math -fno-finite-math-only -pthread -march=core2 -mtune=corei7 -g -O3 -Qunused-arguments -fnon-call-exceptions -fvisibility=hidden -fvisibility-inlines-hidden -Wall -Wextra -Wshadow -Wpointer-arith -Wno-self-assign -Wno-unused-function -Wno-gnu-empty-initializer -Wno-unused-parameter -Wno-ignored-qualifiers -Wno-mismatched-tags -Wno-unused-local-typedef -Wno-parentheses-equality -Wno-unused-private-field -Wno-missing-field-initializers -Wno-missing-braces -Werror=return-type -Werror=overloaded-virtual -DSTRATEGY_BUILD_PROFILE=\"release\" ../../../../shared/Helpers.cpp > .deps/Helpers.o.d
../../../../shared/Helpers.cpp:14:10: fatal error: 'algorithm' file not found
#include <algorithm>
What sets the location path to search for C++ header files, such as algorithm? Is there anything I can grep for within makefiles?
Either install g++ alongside (you need libstdc++) or use LLVM libc++ and specify it with -stdlib=libc++

g++ not suppressing warnings

I am facing the weirdest thing ever. I am having a deprecation warning although I am using -Wno-deprecated flag with g++.
What am I doing wrong? Should I reorder the flags I am passing to g++?
g++ -fno-strict-aliasing -Wall -D__LINUX__ -DOS_USE_STD_IOSTREAMS -DOS_LINUX_2_2 -D__CPP -D__USE_BSD -DLINUX -Wno-sign-compare -Wno-deprecated -Wno-unused-variable -Wno-write-strings -Wno-unused -DOS_USE_STD_IOSTREAM -m64 -m64 -O3 -Werror
The deprecation warning is specifically about sys_errlist and that I should use stderror or stderror_r.
I have checked the specific header file declraing the function that uses sys_errlist and it doesn't have a diagnostic pragma.
I am using GCC 3.3.1 on a 64 bit RHE4 machine

gcc creates crashing code depending on optimisation

I have a rather complex multithreaded code, which I compile using gcc 4.8.1. When compiling with
g++ -c file.cc -march=native -mfpmath=sse -mpreferred-stack-boundary=4
--param inline-unit-growth=50 -ggdb3 -Wall -Wextra -Winit-self
-O2 -fPIC -funroll-loops -fforce-addr -rdynamic
the code produced crashes with segfault (which I was unable to debug, but the address of a struct all of a sudden differs from what it was when constructed, in particular, is no longer aligned to 32bytes as required by the code but only to 8bytes).
When compiling with -O1 instead, the code works fine. I then added all the optimisation flags that make the difference between -O1 and -O2. (To this end, I created two files O1-opts and O2-opts via
g++ -march=native -mfpmath=sse -mpreferred-stack-boundary=4
--param inline-unit-growth=50 -ggdb3 -Wall -Wextra -Winit-self
-O1 -fPIC -funroll-loops -fforce-addr -rdynamic
-Q --help=optimizers > O1-opts
g++ -march=native -mfpmath=sse -mpreferred-stack-boundary=4
--param inline-unit-growth=50 -ggdb3 -Wall -Wextra -Winit-self
-O2 -fPIC -funroll-loops -fforce-addr -rdynamic
-Q --help=optimizers > O2-opts
when diff O1-opts O2-opts provides the option differences). When adding all the option differences to -O1, the code generated still does not crash. This puzzles me. So my question is: shouldn't this give exactly the same result as with -O2? (and also: what is the likely cause of my problem?)
The point is that the -O2 option not only sets different flags, but also enables additional optimizations in contrast to -O1.
The FAQ section of the GCC Wiki has an appropriate entry for this.