I am compiling the following code using clang 3.4.2 ..
#include <stdio.h>
void haa(int& j){
j=1;
}
int main(){
printf("hello\n");
}
This gives the following error:
hello.c:3:13: error: expected ')'
void haa(int& j){
^
hello.c:3:9: note: to match this '('
void haa(int& j){
^
hello.c:3:13: error: parameter name omitted
void haa(int& j){
^
hello.c:4:2: error: use of undeclared identifier 'j'
j=1;
^
3 errors generated.
Compiling the same with gcc gives no errors or warnings...
Can someone explain why this is happening?
The issue is that pass by reference (with references and not pointers) is not a c but a c++ feature.
You need to compile the code with a c++ compiler such as g++ or clang++. Changing the file extension to .cpp also works, as this tells the compiler to treat it as a c++.
Related
int main()
{
auto k = int();//ok
auto i = unsigned int();//gcc error
return 0;
}
The line of "auto i" leads to gcc reporint an eror:
error: expected primary-expression before 'unsigned'
While VC doesn't have problem on my code. Why is this, is this a bug of gcc or, should it use some extra parences?
Thanks.
Does gcc's inline __attribute__((__always_inline__)) generate warning, when compiler can't inline function?
Because VS does http://msdn.microsoft.com/en-us/library/z8y1yy88.aspx:
If the compiler cannot inline a function declared with __forceinline,
it generates a level 1 warning.
You need -Winline to get warnings about non-inlined functions.
If you want to verify this you can try taking the address of an inline function (which prevents it from being inlined) and then you should see a warning.
#include <stdio.h>
static inline __attribute__ ((always_inline)) int add(int a, int b)
{
return a + b;
}
int main(void)
{
printf("%d\n", add(21, 21));
printf("%p\n", add);
return 0;
}
EDIT
I've been trying to produce a warning with the above code and other examples without success - it seems that the behaviour of current versions of gcc and clang may have changed in this area. I'll delete this answer if I can't code up with a better example that generates a warning.
Having trouble compiling the following C++ code on Windows 7:
#include <boost/asio.hpp>
#include <iostream>
void handler1(const boost::system::error_code &ec)
{
std::cout << "5 s." << std::endl;
}
void handler2(const boost::system::error_code &ec)
{
std::cout << "10 s." << std::endl;
}
int main()
{
boost::asio::io_service io_service;
boost::asio::deadline_timer timer1(io_service, boost::posix_time::seconds(5));
timer1.async_wait(handler1);
boost::asio::deadline_timer timer2(io_service, boost::posix_time::seconds(10));
timer2.async_wait(handler2);
io_service.run();
}
I have MinGW installed (gcc 4.8.1) in c:\mingw with my PATH set up correctly. I have downloaded boost and declared environment variable BOOST_ROOT to be the path where it resides. I have gone through the bootstrap and b2 procedure for boost. I now try and compile:
c:\path\to\sandbox> g++ -I%BOOST_ROOT% -o main main.cpp
Gives a bunch of error: '::UnregisterWaitEx' has not been declared errors
I then search a bit and see I may need to link boost_system. So:
c:\path\to\sandbox> g++ -I%BOOST_ROOT% -lboost_system -o main main.cpp
Same errors. Thought I'd try specify library path. Did a search for boost_system and found static libs (libboost_system-mgw48-mt-1_55.a) in %BOOST_ROOT%/stage/lib. So
c:\path\to\sandbox> g++ -I%BOOST_ROOT% -L%BOOST_ROOT%/stage/lib -lboost_system-mgw48-mt-1_55 -o main main.cpp
Same errors. So I search again and see others suggesting appending a -D-D_WIN32_WINNT=0x0601. So
c:\path\to\sandbox> g++ -I%BOOST_ROOT% -L%BOOST_ROOT%/stage/lib -lboost_system-mgw48-mt-1_55 -o main main.cpp -D_WIN32_WINNT=0x0601
And the inevitable errors:
c:\mingw\include\mswsock.h:125:20: error: 'WSAPOLLFD' was not declared in this scope
int WSAAPI WSAPoll(WSAPOLLFD, ULONG, INT);
^
c:\mingw\include\mswsock.h:125:36: error: expected primary-expression before ',' token
int WSAAPI WSAPoll(WSAPOLLFD, ULONG, INT);
^
c:\mingw\include\mswsock.h:125:41: error: expected primary-expression before ')' token
int WSAAPI WSAPoll(WSAPOLLFD, ULONG, INT);
^
c:\mingw\include\mswsock.h:125:41: error: expression list treated as compound expression in initializer [-fpermissive]
Where am I going wrong?
I went ahead and rebuilt Boost again with b2 toolset=gcc --build-type=complete. Same thing happened. Finally, after all that, it turned out all I needed was to put the linking at the end of the command:
C:\path\to\sandbox> g++ -D_WIN32_WINNT=0x0601 -I%BOOST_ROOT% -L%BOOST_ROOT%\stage\lib -o boosttest boosttest.cpp -lwsock32 -lws2_32 -lboost_system-mgw48-mt-d-1_55
C:\path\to\sandbox> boosttest.exe
5 s.
10 s.
The -D_WIN32_WINNT was still necessary and, for anyone who has skipped the other comments, I had to patch winsock.h as detailed http://sourceforge.net/p/mingw/bugs/1980/. And remember to put %BOOST_ROOT%\stage\lib in your PATH so Windows can find the dll at runtime.
Arduous
I've been working on a C++ project using Boost, and between compiles, I must have upgraded something in boost without meaning to or something, because now Boost dependencies won't compile:
In file included from /usr/include/boost/thread/pthread/mutex.hpp:14:0,
from /usr/include/boost/thread/mutex.hpp:16,
from /usr/include/boost/thread/pthread/thread_data.hpp:12,
from /usr/include/boost/thread/thread.hpp:17,
from /usr/include/boost/thread.hpp:13,
from /blah.h:4,
from bluh.h:3,
from bleh/main.cpp:4:
/usr/include/boost/thread/xtime.hpp:23:5: error: expected identifier before numeric constant
/usr/include/boost/thread/xtime.hpp:23:5: error: expected '}' before numeric constant
/usr/include/boost/thread/xtime.hpp:23:5: error: expected unqualified-id before numeric constant
/usr/include/boost/thread/xtime.hpp:46:14: error: expected type-specifier before 'system_time'
In file included from /usr/include/boost/thread/pthread/mutex.hpp:14:0,
from /usr/include/boost/thread/mutex.hpp:16,
from /usr/include/boost/thread/pthread/thread_data.hpp:12,
from /usr/include/boost/thread/thread.hpp:17,
from /usr/include/boost/thread.hpp:13,
from /blah,
from /bleh,(changed these names, obviously)
from /bluh /main.cpp:4:
/usr/include/boost/thread/xtime.hpp: In function 'int xtime_get(xtime*, int)':
/usr/include/boost/thread/xtime.hpp:73:40: error: 'get_system_time' was not declared in this scope
/usr/include/boost/thread/xtime.hpp:73:40: note: suggested alternative:
/usr/include/boost/thread/thread_time.hpp:19:24: note: 'boost::get_system_time'
/usr/include/boost/thread/xtime.hpp: At global scope:
/usr/include/boost/thread/xtime.hpp:88:1: error: expected declaration before '}' token
make[2]: *** [CMakeFiles/edge_based_tracker.dir/main.o] Error 1
make[1]: *** [CMakeFiles/edge_based_tracker.dir/all] Error 2
make: *** [all] Error 2
Any ideas? I tried changing TIME_UTC to TIME_UTC_ as this was recommended to me on another site, but that didn't seem to help.
EDIT: The Boost Version is Version: 1.48.0.2. I've attached xtime below:
// Copyright (C) 2001-2003
// William E. Kempf
// Copyright (C) 2007-8 Anthony Williams
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_XTIME_WEK070601_HPP
#define BOOST_XTIME_WEK070601_HPP
#include <boost/thread/detail/config.hpp>
#include <boost/cstdint.hpp>
#include <boost/thread/thread_time.hpp>
#include <boost/date_time/posix_time/conversion.hpp>
#include <boost/config/abi_prefix.hpp>
namespace boost {
enum xtime_clock_types
{
TIME_UTC=1 //LINE 23
// TIME_TAI,
// TIME_MONOTONIC,
// TIME_PROCESS,
// TIME_THREAD,
// TIME_LOCAL,
// TIME_SYNC,
// TIME_RESOLUTION
};
struct xtime
{
#if defined(BOOST_NO_INT64_T)
typedef int_fast32_t xtime_sec_t; //INT_FAST32_MIN <= sec <= INT_FAST32_MAX
#else
typedef int_fast64_t xtime_sec_t; //INT_FAST64_MIN <= sec <= INT_FAST64_MAX
#endif
typedef int_fast32_t xtime_nsec_t; //0 <= xtime.nsec < NANOSECONDS_PER_SECOND
xtime_sec_t sec;
xtime_nsec_t nsec;
operator system_time() const
{
return boost::posix_time::from_time_t(0)+
boost::posix_time::seconds(static_cast<long>(sec))+
#ifdef BOOST_DATE_TIME_HAS_NANOSECONDS
boost::posix_time::nanoseconds(nsec);
#else
boost::posix_time::microseconds((nsec+500)/1000);
#endif
}
};
inline xtime get_xtime(boost::system_time const& abs_time)
{
xtime res;
boost::posix_time::time_duration const time_since_epoch=abs_time-boost::posix_time::from_time_t(0);
res.sec=static_cast<xtime::xtime_sec_t>(time_since_epoch.total_seconds());
res.nsec=static_cast<xtime::xtime_nsec_t>(time_since_epoch.fractional_seconds()*(1000000000/time_since_epoch.ticks_per_second()));
return res;
}
inline int xtime_get(struct xtime* xtp, int clock_type)
{
if (clock_type == TIME_UTC)
{
*xtp=get_xtime(get_system_time());
return clock_type;
}
return 0;
}
inline int xtime_cmp(const xtime& xt1, const xtime& xt2)
{
if (xt1.sec == xt2.sec)
return (int)(xt1.nsec - xt2.nsec);
else
return (xt1.sec > xt2.sec) ? 1 : -1;
}
} // namespace boost
#include <boost/config/abi_suffix.hpp>
#endif //BOOST_XTIME_WEK070601_HPP
EDIT: To make it clear, the code is failing on an import of boost/thread.hpp
For those running into the same issue and struggling to find the solution here.
Derived from noodlebox' link (https://svn.boost.org/trac/boost/ticket/6940):
You can edit /usr/include/boost/thread/xtime.hpp (or whereever your xtime.hpp lies)
and change all occurrences of TIME_UTC to TIME_UTC_ - Probably around lines 23 and 71.
i.e. sed -i 's/TIME_UTC/TIME_UTC_/g' /usr/include/boost/thread/xtime.hpp
If you're getting syntax errors when using Boost, you may need to compile your code with -std=c++11.
The TIME_UTC issue you might have read about is a side effect of using c++11. TIME_UTC is now defined as a macro in c++11, so you will need to either replace all instances of TIME_UTC with TIME_UTC_, or just use a newer (1.50.0+) version of Boost where this has been fixed already.
See: https://svn.boost.org/trac/boost/ticket/6940
Since you do not show your code, we can only guess. My guess is that you define TIME_UTC macro somewhere in your code. This macro messes-up xtime.hpp header.
I have written some code but it doesn't seem to work when I compile it. I am trying to run this in Ubuntu:
#include <pthread.h>
#include <ctype.h>
#include <unistd.h>
char buffer[128];
void *write_thread(void *args)
{
int count = *((int*)args);
write(STDOUT_FILENO, buffer, count);
pthread_exit(0);
}
void *toupper_thread(void *args)
{
int i;
int count = *((int*)args);
for(i = 0; i < count; i++) {
buffer[i] = toupper(buffer[i]);
}
pthread_t writeId;
pthread_create(&writeId, NULL, write_thread, &count);
pthread_join(writeId, NULL);
pthread_exit(0);
}
void *read_thread(void *args)
{
int count = read(STDIN_FILENO, buffer, 128);
pthread_t toupperId;
pthread_create(&toupperId, NULL, toupper_thread, &count);
pthread_join(toupperId, NULL);
//buffer[count] = 0;
pthread_exit(0);
}
int main()
{
pthread_t threadId;
pthread_create(&threadId, NULL, read_thread, NULL);
pthread_join(threadId, NULL);
}
and I get these errors when I try to compile it with gcc -pthread prob41.c or with gcc prob41.c -lpthread:
prob41.c:1:21: error: pthread.h: No such file or directory
prob41.c: In function ‘toupper_thread’:
prob41.c:23: error: ‘pthread_t’ undeclared (first use in this function)
prob41.c:23: error: (Each undeclared identifier is reported only once
prob41.c:23: error: for each function it appears in.)
prob41.c:23: error: expected ‘;’ before ‘writeId’
prob41.c:24: error: ‘writeId’ undeclared (first use in this function)
prob41.c: In function ‘read_thread’:
prob41.c:33: error: ‘pthread_t’ undeclared (first use in this function)
prob41.c:33: error: expected ‘;’ before ‘toupperId’
prob41.c:34: error: ‘toupperId’ undeclared (first use in this function)
prob41.c: In function ‘main’:
prob41.c:45: error: ‘pthread_t’ undeclared (first use in this function)
prob41.c:45: error: expected ‘;’ before ‘threadId’
prob41.c:46: error: ‘threadId’ undeclared (first use in this function)
I don't know what I'm doing wrong.
It seems that you missed some dependencies.
Try this:
$ sudo apt-get install -y libc6-dev
Need to add -I flag in the compile command to enable the compiler to find pthread.h
You don't have a pthread.h library in the system. Try to install the
suitable library for it.
You need to be sure to use #include <sys/type.h>
Don't forget to add the -lpthread while compiling: gcc -lpthread {x}.c -o {y}