No Emscripten, How to Compile C++ With Standard Library to WebAssembly - c++

I am having trouble building standalone webassembly with the full control I want over memory and layout. I don't want to use emscripten because, as the following post says, it doesn't give me all of the compile-time options I want (e.g. stack size control, being able to choose to import memory in standalone mode, etc.) I've been folowing pages such as: How to generate standalone webassembly with emscripten
Also, emscripten is overkill.
What I've done so far:
I have a fully working llvm 9 toolchain downloaded via homebrew (I am on macos 10.14.)
I was following a mix of https://aransentin.github.io/cwasm/ and https://depth-first.com/articles/2019/10/16/compiling-c-to-webassembly-and-running-it-without-emscripten/
I used wasi to get the C standard library. Using linker flags like -Wl,-z,stack-size=$[1024 * 1024] I could control the stack size. Compilation was successful. Great!
However, I need to use C++ standard libraries to support some of my own and other third party libraries.
As far as I can tell, there doesn't seem to be any easy way to get libc++ and libc++abi.
I tried a "hack" in which I downloaded Emscripten and had it build its own libc++ and libc++abi files. Then I tried copying those files and headers into the right spot.
Then I got error messages referring to a missing threading API, which apparently were caused by not compiling with EMSCRIPTEN. So I defined the EMSCRIPTEN macro and that sort of worked. Then I thought that maybe I could remove the wasi dependency and use emscripten's version of libc to be consistent, but then there were conflicting / missing headers too.
In short, I think I got somewhat close to where I needed to be, but things just got terribly messy. I doubt I took the simplest non-emscripten approach.
Has anyone successfully created a build system for standalone webassembly that lets you use the c and c++ standard libraries?
EDIT:
This is the super hacky build script I have now (it's a heavily modified version of something I found online):
DEPS =
OBJ = library.o
STDLIBC_OBJ = $(patsubst %.cpp,%.o,$(wildcard stdlibc/*.cpp))
OUTPUT = library.wasm
DIR := ${CURDIR}
COMPILE_FLAGS = -Wall \
--target=wasm32-unknown-wasi \
-Os \
-D __EMSCRIPTEN__ \
-D _LIBCPP_HAS_NO_THREADS \
-flto \
--sysroot ./ \
-std=c++17 \
-ffunction-sections \
-fdata-sections \
-I./libcxx/ \
-I./libcxx/support/xlocale \
-I./libc/include \
-DPRINTF_DISABLE_SUPPORT_FLOAT=1 \
-DPRINTF_DISABLE_SUPPORT_LONG_LONG=1 \
-DPRINTF_DISABLE_SUPPORT_PTRDIFF_T=1
$(OUTPUT): $(OBJ) $(NANOLIBC_OBJ) Makefile
wasm-ld \
-o $(OUTPUT) \
--no-entry \
--export-all \
--initial-memory=131072 \
--stack-size=$[1024 * 1024] \
-error-limit=0 \
--lto-O3 \
-O3 \
-lc -lc++ -lc++abi \
--gc-sections \
-allow-undefined-file ./stdlibc/wasm.syms \
$(OBJ) \
$(LIBCXX_OBJ) \
$(STDLIBC_OBJ)
%.o: %.cpp $(DEPS) Makefile
clang++ \
-c \
$(COMPILE_FLAGS) \
-fno-exceptions \
-o $# \
$<
library.wat: $(OUTPUT) Makefile
~/build/wabt/wasm2wat -o library.wat $(OUTPUT)
wat: library.wat
clean:
rm -f $(OBJ) $(STDLIBC_OBJ) $(OUTPUT) library.wat
I dropped-in libc, libc++, and libc++abi from emscripten (but honestly this is a terrible installation process.)
I've been incrementally trying to fill in gaps that I guess emscripten would've normally done, but now I'm stuck again:
./libcxx/type_traits:4837:57: error: use of undeclared identifier 'byte'
constexpr typename enable_if<is_integral_v<_Integer>, byte>::type &
^
./libcxx/type_traits:4837:64: error: definition or redeclaration of 'type'
cannot name the global scope
constexpr typename enable_if<is_integral_v<_Integer>, byte>::type &
I am no longer sure if this will even work since the system might accidentally compile something platform-specific in. Really what I'd like is a shim that would just let me use the standard containers mostly.
This has become kind of unmanageable. What might I do next?
EDIT 2: Right so that's missing C++17 type trait content, and when I go to C++14 (I still want C++17) I end up with more missing things.
Definitely stuck.
EDIT 3:
I sort of started over. The libraries are linking, and I'm able to use the standard, but I'm seeing errors like the following if I try to use e.g. an std::chrono's methods (I can instantiate the object):
wasm-ld: error: /var/folders/9k/zvv02vlj007cc0pm73769y500000gn/T/library-4ff1b5.o: undefined symbol: std::__1::chrono::system_clock::now()
I'm currently using the static library abi from emscripten and the static library C++ standard library from my homebrew installation of llvm (I tried the emscripten one but that didn't work either).
I'm not really sure if this is related to name mangling. I'm currently exporting all symbols from webasm so malloc and co. get exported as well.
Here is my build script:
clang++ \
--target=wasm32-unknown-wasi \
--std=c++11 \
-stdlib=libc++ \
-O3 \
-flto \
-fno-exceptions \
-D WASM_BUILD \
-D _LIBCPP_HAS_NO_THREADS \
--sysroot /usr/local/opt/wasi-libc \
-I/usr/local/opt/wasi-libc/include \
-I/usr/local/opt/glm/include \
-I./libcxx/ \
-L./ \
-lc++ \
-lc++abi \
-nostartfiles \
-Wl,-allow-undefined-file wasm.syms \
-Wl,--import-memory \
-Wl,--no-entry \
-Wl,--export-all \
-Wl,--lto-O3 \
-Wl,-lc++, \
-Wl,-lc++abi, \
-Wl,-z,stack-size=$[1024 * 1024] \
-o library.wasm \
library.cpp
My code:
#include "common_header.h"
#include <glm/glm.hpp>
#include <unordered_map>
#include <vector>
#include <string>
#include <chrono>
template <typename T>
struct BLA {
T x;
};
template <typename T>
BLA<T> make_BLA() {
BLA<T> bla;
std::unordered_map<T, T> map;
std::vector<T> bla2;
std::string str = "WEE";
//str = str.substr(0, 2);
return bla;
}
#ifdef __cplusplus
extern "C" {
#endif
char* malloc_copy(char* input)
{
usize len = strlen(input) + 1;
char* result = (char*)malloc(len);
if (result == NULL) {
return NULL;
}
strncpy(result, input, len);
return result;
}
void malloc_free(char* input)
{
free(input);
}
float32 print_num(float val);
float32 my_sin(float32 val)
{
float32 result = sinf(val);
float32 result_times_2 = print_num(result);
print_num(result_times_2);
return result;
}
long fibonacci(unsigned n) {
if (n < 2) return n;
return fibonacci(n-1) + fibonacci(n-2);
}
void set_char(char* input)
{
input[0] = '\'';
uint8 fibonacci_series[] = { 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 };
for (uint8 number : fibonacci_series) {
input[0] = number;
}
auto WEE = make_BLA<int>();
WEE.x = 18;
glm::vec4 v(100.0f, 200.0f, 300.0f, 1.0f);
glm::vec4 v_out = glm::mat4(1.0f) * v;
input[0] = 5 + static_cast<int>(v_out.x) * input[1];
auto start = std::chrono::system_clock::now();
long out = fibonacci(42);
auto end = std::chrono::system_clock::now();
std::chrono::duration<double> elapsed_seconds = end-start;
std::time_t end_time = std::chrono::system_clock::to_time_t(end);
auto elapsed = elapsed_seconds.count();
}
#ifdef __cplusplus
}
#endif
When I tried exporting dynamically with the "visible" attribute on only the functions that had no C++, the project compiled, but the wasm module failed to load in JavaScript, so I think the problem was still there.
This is as far as I've gotten. Might the issue be related to the fact that I'm using a different compiler from the one used to create the static libraries? (I'm using homebrew clang 9). Hopefully not. I'd be kind of stuck then because I couldn't find another way to get the libraries. Manual llvm compilation seemed to fail.

The excellent wasi-sdk pulls upstream llvm-project (which provides clang++) and wasi-libc as git submodules and compiles them using suitable flags (most notably disabling pthreads which is not yet supported in wasi-libc).
You can then compile your own C++ source using the following minimal set of options:
/path/to/wasi-sdk/build/install/opt/wasi-sdk/bin/clang++ \
-nostartfiles \
-fno-exceptions \
-Wl,--no-entry \
-Wl,--strip-all \
-Wl,--export-dynamic \
-Wl,--import-memory \
-fvisibility=hidden \
--sysroot /path/to/wasi-sdk/build/install/opt/wasi-sdk/share/wasi-sysroot \
-o out.wasm \
source.cpp
If you want to import functions from the runtime, I would suggest adding an additional line:
-Wl,--allow-undefined-file=wasm-import.syms \
You then can put function names separated by newlines into wasm-import.syms so that the linker won't complain about undefined functions.
Note that all this is completely independent of Emscripten.

Related

LLVM build error due to no matching function

I cloned the LLVM git repositories and followed https://llvm.org/docs/GettingStarted.html. After configuration with
cmake $SOURCEDIR -G "Unix Makefiles" \
-DCLANG_DEFAULT_CXX_STDLIB=libc++ \
-DC_INCLUDE_DIRS=:/usr/include \
-DLLVM_ENABLE_WERROR=OFF \
-DCMAKE_BUILD_TYPE=DEBUG \
-DCMAKE_C_COMPILER=$CC \
-DCMAKE_CXX_COMPILER=$CXX \
-DCMAKE_EXE_LINKER_FLAGS="${LDFLAGS}" \
-DCMAKE_CXX_FLAGS_RELEASE="${CXXFLAGS}" \
-DCMAKE_INSTALL_PREFIX=$INSTALLDIR \
-DCMAKE_EXPORT_COMPILE_COMMANDS=ON
I tried to build LLVM and Clang with
make -j 24
but it failes (I added new lines for improved readability):
/home/myUserName/LLVM/sources/tools/clang/utils/TableGen/ClangAttrEmitter.cpp:
In constructor ‘{anonymous}::EnumArgument::EnumArgument(const llvm::Record&, llvm::StringRef)’:
/home/myUserName/LLVM/sources/tools/clang/utils/TableGen/ClangAttrEmitter.cpp:740:42:
error: no matching function for call to
‘std::vector<std::__cxx11::basic_string<char> >::vector(std::vector<llvm::StringRef>)’
uniques(uniqueEnumsInOrder(enums))
^
Unfortunately I don't understand why there is a problem, since this function should be declared in
tools/clang/utils/TableGen/ClangAttrEmitter.cpp:722.
This is an excerpt of the corresponding code:
// Unique the enums, but maintain the original declaration ordering.
std::vector<std::string>
uniqueEnumsInOrder(const std::vector<std::string> &enums) {
std::vector<std::string> uniques;
SmallDenseSet<StringRef, 8> unique_set;
for (const auto &i : enums) {
if (unique_set.insert(i).second)
uniques.push_back(i);
}
return uniques;
}
class EnumArgument : public Argument {
std::string type;
std::vector<std::string> values, enums, uniques;
public:
EnumArgument(const Record &Arg, StringRef Attr)
: Argument(Arg, Attr), type(Arg.getValueAsString("Type")),
values(Arg.getValueAsListOfStrings("Values")),
enums(Arg.getValueAsListOfStrings("Enums")),
uniques(uniqueEnumsInOrder(enums))
{
// FIXME: Emit a proper error
assert(!uniques.empty());
}
I use gcc 7.2.0 and Ubuntu 16.04.3 LTS.
Update:
In the meantime I had the chance to build LLVM+Clang with gcc 5.4.0 and the build finished successfully. Does this mean that there is a compiler bug oder is it an issue respectively the gcc standard?

Problems with Boost 1.55 on Mavericks

I upgraded my system to Mac OS 10.9 and spent the whole weekend to get my software working. Without many success though…
Some of the tools I need require boost, however I used boost 1.38 before, which simply does not compile on Mavericks. So I decide to use homebrew to install boost 1.55. The installation went without any problems, but when I try to compile my toolset, it throws me this error:
Syntax error /usr/local/include/boost/exception/exception.hpp:343:
Error: void type variable can not be declared /usr/local/include/boost/smart_ptr/shared_ptr.hpp:243:
Error: void type variable can not be declared /usr/local/include/boost/smart_ptr/shared_ptr.hpp:245:
Error: Invalid type '>{typedef' in declaration of 'boost::exception_detail::error_info_base type;}' /usr/local/include/boost/smart_ptr/shared_ptr.hpp:78:
Error: class,struct,union or type element_type not defined /usr/local/include/boost/smart_ptr/shared_ptr.hpp:439:
Internal error: global function template arg type /usr/local/include/boost/smart_ptr/shared_ptr.hpp:439:
Error: Invalid type '>{typedef' in declaration of 'void type;}' /usr/local/include/boost/smart_ptr/shared_ptr.hpp:127:
Internal warning: >{typedef void type;} comment can not set /usr/local/include/boost/smart_ptr/shared_ptr.hpp:127:
Error: Invalid type '>{typedef' in declaration of 'void type;}' /usr/local/include/boost/smart_ptr/shared_ptr.hpp:152:
...
...
...
Warning: Error occurred during reading source files
Warning: Error occurred during dictionary source generation
Error: rootcint: error loading headers...
make[2]: *** [icetray/CMakeFiles/icetrayDict.cxx] Error 1
make[1]: *** [icetray/CMakeFiles/icetray.dir/all] Error 2
make: *** [all] Error 2
I'm not sure what's wrong and don't have a clue where to start to debug this. Google did not return anything helpful, so I'm really struggling right now.
The header files where installed correctly in /usr/local/Cellar and are linked to /usr/local/include.
Btw. I started with a completely fresh Mavericks install (+ Xcode for the devtools) and only used brew to install some additional packages.
This is the quoted code in exception.hpp:
340: struct large_size { char c[256]; };
341: large_size dispatch_boost_exception( exception const * );
343: struct small_size { };
344: small_size dispatch_boost_exception( void const * );
And the corresponding code from the first Error, in smpart_ptr:
239: #if !defined( BOOST_NO_SFINAE ) && !defined( BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION ) && !defined( BOOST_NO_AUTO_PTR )
241: // rvalue auto_ptr support based on a technique by Dave Abrahams
243: template< class T, class R > struct sp_enable_if_auto_ptr
244: {
245: };
247: template< class T, class R > struct sp_enable_if_auto_ptr< std::auto_ptr< T >, R >
248: {
249: typedef R type;
250: };
252: #endif
Compiler flags:
C_FLAGS = -Wall -Wno-mismatched-tags -Wno-char-subscripts -Wno-unused
-Wunneeded-internal-declaration -Wno-parantheses-equality -g -fPIC -I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/cmake/tool-patches/common
-I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/public -I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/private -I/usr/local/Cellar/boost/1.55.0/include/boost -I/System/Library/Frameworks/Python.framework/Headers -I/Users/tamasgal/Xapps/i3/seaports/include/log4cplus-1.0.2 -I/Users/tamasgal/Xapps/i3/seaports/root-v5.34.12/include/root -fPIC -fno-strict-aliasing -include /Users/tamasgal/Xapps/seatray/searecsim/trunk/build_debug/CMakeFiles/I3.h
C_DEFINES = -DI3_USE_CINT -DI3_USE_ROOT -DPROJECT=icetray
-D_REEENTRANT
CXX_FLAGS = -Wall -Wno-non-virtual-dtor -Wno-mismatched-tags
-Wno-char-subscripts -Wno-unused -Wunneeded-internal-declaration -Wno-parantheses-equality -g -fPIC -I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/cmake/tool-patches/common
-I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/public -I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/private -I/usr/local/Cellar/boost/1.55.0/include/boost -I/System/Library/Frameworks/Python.framework/Headers -I/Users/tamasgal/Xapps/i3/seaports/include/log4cplus-1.0.2 -I/Users/tamasgal/Xapps/i3/seaports/root-v5.34.12/include/root -fPIC -fno-strict-aliasing -include /Users/tamasgal/Xapps/seatray/searecsim/trunk/build_debug/CMakeFiles/I3.h
CXX_DEFINES = -DI3_USE_CINT -DI3_USE_ROOT -DPROJECT=icetray
-D_REEENTRANT
rootcint build command:
cd /Users/tamasgal/Xapps/seatray/searecsim/trunk/build_debug/icetray && \
../env-shell.sh rootcint -f \
/Users/tamasgal/Xapps/seatray/searecsim/trunk/build_debug/icetray/CMakeFiles/icetrayDict.cxx -c -DI3_USE_ROOT -DI3_USE_CINT \
-I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/cmake/tool-patches/common \
-I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/public \
-I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/private \
-I/usr/local/Cellar/boost/1.55.0/include/boost \
-I/System/Library/Frameworks/Python.framework/Headers \
-I/Users/tamasgal/Xapps/i3/seaports/include/log4cplus-1.0.2 \
-I/Users/tamasgal/Xapps/i3/seaports/root-v5.34.12/include/root \
-I/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/public \
-p /Users/tamasgal/Xapps/seatray/searecsim/trunk/build_debug/CMakeFiles/I3.h \
/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/public/icetray/I3FrameObject.h \
/Users/tamasgal/Xapps/seatray/searecsim/trunk/src/icetray/LinkDef.h
Relevant code part from I3.h:
#define BOOST_NO_WREGEX
#ifdef I3_OPTIMIZE
#define BOOST_DISABLE_ASSERTS
#endif
#include <boost/version.hpp>
#include <boost/shared_ptr.hpp>
using boost::shared_ptr;
using boost::dynamic_pointer_cast;
// workaround for braindead rootcint. doesn't recognize the using
// boost::shared_ptr. I can just see this popping up to cause us
// unspeakable aggravation in the future...
#ifdef __CINT__
template <typename T>
struct shared_ptr : boost::shared_ptr<T> { };

Autoconf with boost test - linker issue

I'm facing an issue with boost unit_test framework along with autoconf & automake...
Here's about the project structure:
./include/com_i_foo.h
./include/com_foo.h
...
class FooSingleton {
protected:
FooSingleton() {}
private:
FooSingleton* _instance;
public:
virtual ~FooSingleton() {}
static FooSingleton* getInstance();
};
class FooFoo {
public:
FooFoo() {}
virtual uint32_t getSomeInt();
virtual ~FooFoo() {}
};
typedef boost::shared_ptr FooFooPtr_t;
...
./include/com_api.h
#include "com_foo.h"
./include/Makefile.am
include_HEADERS = \
com_i_foo.h \
com_foo.h \
com_api.h \
$(NULL)
./src/com_foo.cpp
./src/Makefile.am
PLATEFORM=LINUX64
DEBUG_OPTIONS = -g
DEFINE_OPTIONS=-D${PLATEFORM}
OPTIONS = -Wall -Werror -shared -O2 $(DEBUG_OPTIONS) $(DEFINE_OPTIONS)
COMMON_CXXFLAGS= ${OPTIONS} -I$(top_builddir)/include
ACLOCAL_AMFLAGS = -I ${top_builddir}/m4
AM_LDFLAGS=
lib_LTLIBRARIES = \
libcom_api.la \
$(NULL)
libcom_api_la_SOURCES = com_foo.cpp
libcom_api_la_CXXFLAGS = ${COMMON_CXXFLAGS}
libcom_api_la_LDFLAGS =
libcom_api_la_LIBADD =
./test/Makefile.am
PLATEFORM=LINUX64
DEBUG_OPTIONS = -g
DEFINE_OPTIONS=-D${PLATEFORM} -DBOOST_ENABLE_ASSERT_HANDLER
OPTIONS = -Wall -Werror -O2 $(DEBUG_OPTIONS) $(DEFINE_OPTIONS)
BOOST_LIBS = -lboost_unit_test_framework -lboost_locale -lboost_filesystem -lboost_system -lboost_thread
COMMON_CXXFLAGS= ${OPTIONS} -I$(top_srcdir)/include -I$(top_srcdir)/src
AM_LDFLAGS=
ACLOCAL_AMFLAGS = -I ${top_builddir}/m4
check_PROGRAMS = ut_com_api
ut_com_api_SOURCES = \
ut_com_api.cpp \
$(NULL)
ut_com_api_CXXFLAGS = ${COMMON_CXXFLAGS}
ut_com_api_LDFLAGS = -rdynamic
ut_com_api_LDADD = ${BOOST_LIBS} $(top_builddir)/src/libcom_api.la
./test/ut_com_api.cpp
#define BOOST_LIB_DIAGNOSTIC
#define BOOST_TEST_DYN_LINK
#define BOOST_TEST_MODULE "Common API Unit tests"
#include
#include "com_api.h"
using namespace boost::unit_test;
BOOST_AUTO_TEST_SUITE(com_api)
BOOST_AUTO_TEST_CASE(FooFooTest) {
FooFooPtr_t myFoo(new FooFoo());
BOOST_CHECK(myFoo->getSomeInt() == 2);
}
BOOST_AUTO_TEST_CASE(FooSingletonTest) {
FooSingleton* myFoo = FooSingleton::getInstance();
BOOST_CHECK(myFoo != NULL);
}
BOOST_AUTO_TEST_SUITE_END()
./Makefile.am
SUBDIRS = include src test
#dist_doc_DATA = README
ACLOCAL_AMFLAGS = -I m4
./configure.ac
AC_INIT([com_api], [1.0], [bug#foo.foo])
AC_CONFIG_MACRO_DIR([m4])
AM_INIT_AUTOMAKE([-Wall -Werror foreign])
AC_PROG_LIBTOOL
AC_PROG_CXX
AC_LANG_PUSH(C++)
AX_BOOST_BASE([1.53], ,[AC_MSG_ERROR([You need boost library])])
AX_BOOST_PROGRAM_OPTIONS
AX_BOOST_DATE_TIME
AC_CHECK_HEADER([boost/shared_ptr.hpp], , [AC_MSG_ERROR([You need boost library])])
AC_LANG_POP(C++)
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([
Makefile
include/Makefile
src/Makefile
test/Makefile
])
AC_OUTPUT
My Problem:
When I build the DLL (.so under linux) it works perfectly, but when I try to build the check_PROGRAMS, the linker returns the following undefined references:
undefined reference to FooSingleton::_instance
In function `boost::shared_ptr::operator->() const':
undefined reference to boost::assertion_failed(char const*, char const*, char const*, long)
About FooSingleton, I don't understand why because I'm well linking my check program with the built dll...
About boost, I guess I'm lacking a -lboost_xxxx in my test/Makefile.am, but I don't get why I'd have to explicitly specify boost libs to the linker for check_PROGRAMS while it works perfectly with the DLL build...
I've looked everywhere for a solution, but I'm running out of ideas so any help would be appreciated!
It looks like the macro BOOST_ENABLE_ASSERT_HANDLER is somehow being defined.
As stated in the documentation for Boost.Assert, if BOOST_ENABLE_ASSERT_HANDLER is defined when <boost/assert.hpp> is included, then BOOST_ASSERT(expr) expands to a call to boost::assertion_failed, but this function is not implemented; the user is expected to provide an implementation.
Try to see if something is causing BOOST_ENABLE_ASSERT_HANDLER to be defined when building check_PROGRAMS.

Automatic vectorization GCC

I'm trying to get GCC 4.7 to automatically vectorize some parts of my code to provide a speed increase, however, it seems difficult to do so.
Here some code that I would like to vectorize:
void VideoLine::WriteOut(unsigned short * __restrict__ start_of_line, const int number_of_sub_pixels_to_write)
{
unsigned short * __restrict__ write_pointer = (unsigned short *)__builtin_assume_aligned (start_of_line, 16);
unsigned short * __restrict__ line = (unsigned short *)__builtin_assume_aligned (_line, 16);
for (int i = 0; i < number_of_sub_pixels_to_write; i++)
{
write_pointer[i] = line[i];
}
}
I am using the following GCC switches:
-std=c++0x \
-o3 \
-msse \
-msse2 \
-msse3 \
-msse4.1 \
-msse4.2 \
-ftree-vectorizer-verbose=5\
-funsafe-loop-optimizations\
-march=corei7-avx \
-mavx \
-fdump-tree-vect-details \
-fdump-tree-optimized \
I'm aware that some override others.
I do not get any output from the vectorizer at all, however, when looking at the .optomized file, I can see it has not used vectorization. Can anyone point me in the right way to get this to vectorize?
Edit: Turned out the issue was using -o3 rather than -O3.
try to guarantee, that number_of_sub_pixels_to_write is a multiple of 4 by masking it like the way it is done here:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dht0002a/ch01s04s03.html
The compiler is free to do what it pleases. Therefore, if you really want to use SIMD functionality (and not rely on the compiler), you should use the functions (see the manual).

Using sem_t in a Qt Project

I'm working on a simulation in Qt (C++), and would like to make use of a Semaphore wrapper class I made for the sem_t type.
Although I am including semaphore.h in my wrapper class, running qmake provides the following error:
'sem_t does not name a type'
I believe this is a library/linking error, since I can compile the class without problems from the command line.
I've read that you can specify external libraries to include during compilation. However, I'm a) not sure how to do this in the project file, and b) not sure which library to include in order to access semaphore.h.
Any help would be greatly appreciated.
Thanks,
Tom
Here's the wrapper class for reference:
Semaphore.h
#ifndef SEMAPHORE_H
#define SEMAPHORE_H
#include <semaphore.h>
class Semaphore {
public:
Semaphore(int initialValue = 1);
int getValue();
void wait();
void post();
private:
sem_t mSemaphore;
};
#endif
Semaphore.cpp
#include "Semaphore.h"
Semaphore::Semaphore(int initialValue) {
sem_init(&mSemaphore, 0, initialValue);
}
int Semaphore::getValue() {
int value;
sem_getvalue(&mSemaphore, &value);
return value;
}
void Semaphore::wait() {
sem_wait(&mSemaphore);
}
void Semaphore::post() {
sem_post(&mSemaphore);
}
And, the QT Project File:
TARGET = RestaurantSimulation
TEMPLATE = app
QT +=
SOURCES += main.cpp \
RestaurantGUI.cpp \
RestaurantSetup.cpp \
WidgetManager.cpp \
RestaurantView.cpp \
Table.cpp \
GUIFood.cpp \
GUIItem.cpp \
GUICustomer.cpp \
GUIWaiter.cpp \
Semaphore.cpp
HEADERS += RestaurantGUI.h \
RestaurantSetup.h \
WidgetManager.h \
RestaurantView.h \
Table.h \
GUIFood.h \
GUIItem.h \
GUICustomer.h \
GUIWaiter.h \
Semaphore.h
FORMS += RestaurantSetup.ui
LIBS +=
Full Compiler Output:
g++ -c -pipe -g -gdwarf-2 -arch i386 -Wall -W -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -
I/usr/local/Qt4.6/mkspecs/macx-g++ -I. -
I/Library/Frameworks/QtCore.framework/Versions/4/Headers -I/usr/include/QtCore -
I/Library/Frameworks/QtGui.framework/Versions/4/Headers -I/usr/include/QtGui -
I/usr/include -I. -I. -F/Library/Frameworks -o main.o main.cpp
In file included from RestaurantGUI.h:10,
from main.cpp:2:
Semaphore.h:14: error: 'sem_t' does not name a type
make: *** [main.o] Error 1
make: Leaving directory `/Users/thauburger/Desktop/RestaurantSimulation'
Exited with code 2.
Error while building project RestaurantSimulation
When executing build step 'Make'
I was able to compile and link your semaphore class using qmake without any unexpected steps (including linking in the rt or pthread libraries). I created the following main:
#include "Semaphore.h"
int main(int argc, char* argv[])
{
Semaphore sem;
return 0;
}
And then I generated the following project file using qmake -project:
######################################################################
# Automatically generated by qmake (2.01a) Mon May 24 12:50:02 2010
######################################################################
TEMPLATE = app
TARGET =
DEPENDPATH += .
INCLUDEPATH += .
# Input
HEADERS += Semaphore.h
SOURCES += main.cpp Semaphore.cpp
Whatever error you're seeing is caused by something other than your Semaphore class. I'd recommend taking a good look at your RestaurantGUI.h file. You may need to take a look at the preprocessed output (gcc's -E flag) in order to see what's really happening.
NOTE: I'd recommend renaming your semaphore files to something that will work on case-insensitive filesystems, such as Windows.
Why don't you use semaphore mechanism provided by the Qt framework? I'd use QSemaphores just to stay within Qt ecosystem.
QMake adds external include path using INCLUDEPATH
like INCLUDEPATH += include_dir
What is your INCLUDEPATH set to in the pro file?