All Questions
1,685 questions
1
vote
1
answer
146
views
Does std::unique_ptr support fancy pointers?
Can std::unique_ptr manage pointers only, or fancy pointers (pointer-like types) too?
I assume "fancy pointers too", because for resources like files/sockets, fancy pointers can be a great ...
- 323
0
votes
0
answers
84
views
Fixing a complicated class w/union + struct
I have a somewhat complex class that compiles with Visual Studio 2019 with no issues. I'm trying to compile it now in GCC. It gives me an error because I'm using a class within an anonymous union, ...
- 672
1
vote
2
answers
140
views
Why exception can not be caught on windows by msvc but on Linux by GCC [duplicate]
The same files on Windows and Linux as follow:
std_exp.cpp
#include <iostream>
#include <string>
#include <stdexcept>
using namespace std;
int main() {
try {
std::...
0
votes
1
answer
48
views
Unexpected output of C++11 regex?
#include <iostream>
#include <regex>
#include <string>
#include <vector>
using namespace std;
#define debug(exp) do { cout << #exp << ": " << (exp) &...
- 1
0
votes
0
answers
53
views
How can I force g++ 5.4.0 to only use system headers that do not require C++11 support?
I am compiling C and C++ code for several platforms using Docker images provided by a different team. The other team provides different Docker images for each platform, and there is no uniformity as ...
- 4,680
8
votes
1
answer
122
views
Replacing throw(...) with noexcept(...) - ABI safe across language standards?
Suppose I'm using a library that has a declaration like this in its header:
#if __cplusplus >= 201703L
// C++17 or newer
#define _NOTHROW noexcept(true)
#define _THROWS(x) noexcept(false)
#...
- 348
0
votes
1
answer
110
views
Why does the function recursion seem to make the conditions work crazily?
First at all:
test_container, in the following code, is a function that is only used for "debugging" purposes. There is no real use on my working project.
The real function is called ...
2
votes
0
answers
102
views
Prevent reordering of prefetch instruction in c++
Usecase: I have an SPSC queue in multi-thread setup, where I want to prefetch the write_index's mempool on a successful pop.
Following is my original implementation:
void process()
{
if(spsc_queue-&...
- 969
0
votes
0
answers
99
views
Re-implementation of strptime in C++11 leads to strange behavior with VisualStudio
In order to have a fully portable code Win/Linux,
I tried to re-implement a strptime like function using C++11 and all the hints I found on stackoverflow (and others).
But I see a strange behaviors (...
- 527
0
votes
2
answers
441
views
With C++11, how can I generate a warning message in a manner that works in gcc, clang, and MSVC?
When compiling C++11 using clang or gcc, I can generate a warning message at compilation time using:
#warning My message here
This doesn't work on Windows when I use MSVC, though. How can I ...
- 2,120
2
votes
0
answers
213
views
How to suppress warning -Wignored-attributes using __m128 on templates?
I've this basic code:
#include <iostream>
#include <emmintrin.h>
template <typename T>
struct SRCDecimator {
SRCDecimator() {
}
};
int main()
{
SRCDecimator<__m128&...
- 47.8k
1
vote
0
answers
100
views
Why is compiler mis-stating namespace?
Doing some C++ development after a good four years in Python, it appears I'm a little rusty.
I have three files in my very cut-down example (the actual code is much larger but this example still ...
- 879k
0
votes
1
answer
116
views
Why gcc does not create a new variable?
I have such code:
static const char kFmt[] = "some string: - %s";
char buf[sizeof(kFmt) + 10];
snprintf(buf, sizeof(buf), kFmt, "string");
It looks like arm gcc 6.3.0 does not ...
- 1,013
4
votes
1
answer
133
views
Why does the correct implementation of std::addressof require compiler support?
From possible implementation of std::addressof on https://en.cppreference.com/w/cpp/memory/addressof, it states that "correct implementation of std::addressof require compiler support". Why ...
- 321
0
votes
1
answer
170
views
Error when using C++11 List Initialization Syntax g++ compiler
When I use list initialization to init my class members, the complier complains it's a function.
The g++ output:
$ g++ main.cpp -o main
In file included from main.cpp:1:
./Cat.h:9:9: error: function ...
- 97
1
vote
1
answer
101
views
Why directly modifying basic_string.h does not recompile
I am not so familiar with std containers. It seems basic_string.h is a template and can be modified to use directly without recompile libstdc++.
Am I correct on this?
Thanks for helps.
- 83
2
votes
1
answer
975
views
TWS API Linux - Segmentation fault - __bid64_to_string
Running Cpp sample client out of the box.
I receive a segmentation fault.
0x00005555555efba6 in __bid64_to_string ()
Have sourced this function to client file to Decimal.h
extern "C" void ...
- 1,305
2
votes
1
answer
84
views
condition_variable::wait_until passes through unexpectedly g++ (9.4.0)
I am trying to understand the behaviour of condition_variable::wait_until. I have two pieces of code which I expect will wait one second and then exit. However, when I execute the programs (compiled ...
- 884
0
votes
1
answer
192
views
Old-style vs C++11 attribute syntax
By old-style I mean __attribute__((visibility("default")))
By C++11 syntax I mean [[gnu::visibility("default")]]
I am working on huge codebase which must stay buildable with MSVC, ...
- 9,340
0
votes
0
answers
26
views
gcc compiler not able to find function definition in code file (.cpp)? [duplicate]
I want to compile my C++ code locally. I have separated it into header files (.hpp) and code files (.cpp)
galaxy.hpp
#pragma once
#include <vector>
namespace Edge
{
namespace Galaxy
{
...
4
votes
4
answers
235
views
How to prevent floating-point being implicitly converted to integral value at function call in c++? [duplicate]
How to prevent floating-point being implicitly converted to integral value at function call?
#include <iostream>
void fn(int x) {
std::cout<<"fn("<<x<<")\n&...
- 308
0
votes
0
answers
32
views
When I am running code it is this error how to fix it?
Please help me to resolve this error.
gcc compiler is not working in ventura macOS
. When I am running code it is showing that update your include path. Please help me how gcc will be working in ...
0
votes
1
answer
120
views
Undefined reference to `FastPForLib:..' while linking FastPForlib
Any suggestion regarding the following query would be appreciated. I have tried everything and am still struck with this error. The library (FastPFor) works fine with the visual studio solution; the ...
2
votes
0
answers
626
views
Is this a bug in gcc 11.2.1 related to _GLIBCXX_USE_CXX11_ABI?
The following C++ code fails to compile on gcc 11.2.1 on CentOS 7.2.2009 (available through Software Collections only) using the following command :
Command : scl enable devtoolset-11 'g++ -std=c++11 ...
- 2,734
0
votes
2
answers
4k
views
Cannot install fastText because gcc 7.3.1 does not support C++11 on Amazon Linux
I need to install a system that uses fastText onto an Amazon Linux machine.
As practice, I have been trying to build fastText from source inside an Amazon Linux 2 docker image. I noticed gcc wasn't ...
- 4,877
3
votes
0
answers
310
views
How can I build the boost libraries 1_72_0 on a windows host for a linux target?
Trying to build the boost libraries, I followed the steps:
open cmd in boost_1_72_0 folder
bootstrap.bat gcc
set cfalgs, cxxflags and linker flags to use the sysroot folder that came with the ...
- 187
10
votes
2
answers
227
views
Forward-declaration of enum member of template-specialization - fails with GCC
I know that, generally, we can forward-declare enums in C++11.
So, why does this:
enum kind_t { kind1, kind2 };
template <kind_t Kind> struct foo {};
template <> struct foo<kind1> {...
- 130k
0
votes
1
answer
399
views
Build boost from source with manually built gcc compiler in cluster
I am trying to compile Boost 1.79.0 in a cluster using the GCC compiler version 12.1.0 that I have compiled manually since the GCC version of the cluster is very old.
After compiling GCC, I have ...
5
votes
1
answer
592
views
c++ complains about __VA_ARGS__
The following code has been compiled with gcc-5.4.0 with no issues:
% gcc -W -Wall a.c
...
#include <stdio.h>
#include <stdarg.h>
static int debug_flag;
static void debug(const char *fmt,...
- 6,434
1
vote
1
answer
159
views
Question about std::make_pair & std::atomic_bool
Why this code snippet does not compile with gcc 4.9.0,
whereas it works well with gcc 12.1.
The same code snippet is compiled with the same option.
Here is the code snippet:
#include<atomic>
#...
- 3,424
1
vote
0
answers
123
views
std::regex constructor throwing std::regex_error with what(): regex_error
I need to get some strings from a given line as below:
{"username":"wrongpass", "password":"abc", "email":"[email protected]"}
To be more ...
0
votes
0
answers
22
views
Making a static map with pair as a key [duplicate]
Trying to solve a leetcode problem. Here's the link. In the problem I am trying to make a static map with pair as a key.
As I removed the static keyword, the code is working perfectly fine.
But in ...
- 420
3
votes
1
answer
1k
views
Getting Arduino IDE to compile for C++14
I've been looking to modify the build flags under Arduino's IDE 1.x, or even the Arduino CLI (which I haven't used but am willing to adopt) such that I can undefine -std=gnu++11 and instead define -...
0
votes
0
answers
235
views
Trying to complie ICU by unicode on RHEL7 system
I am trying to install ICU from git clone repo.
I run ./cnfigure and everything seems fine.
When i go to run make I get a bunch of errors.
I am new to Linux and cannot find any fixes anywhere.
it ...
- 1
1
vote
1
answer
117
views
Standard hash with variadic template
I have the following code:
namespace foo {
template<typename ...Types>
class Pi {
};
}
namespace std {
template<> //line offending gcc 8.3.1
template<typename ...Types&...
- 22.2k
1
vote
1
answer
519
views
Get GCC to Remove C++ 11 Flag in Mangled Name
I'm debugging a build that links against JsonCpp and I get a linker error where the demangled name it's trying to link to is _ZNK4Json6Reader25getFormattedErrorMessagesB5cxx11Ev and the one the ...
- 1,093
2
votes
1
answer
77
views
What are the rules for integral promotions in initialization lists and is this a false positive warning in GCC or rather C++ limitation?
In the below code we essentially assign the same value to 4 unsigned char variables in 4 different ways - but one of them using the initialization list issues a warning:
warning: narrowing conversion ...
- 2,115
0
votes
0
answers
63
views
Overload Resolution: Templatized member function vs friend function for stream operator
Suppose we have this scenario(maybe a little bit artificial)
class OStream
{
virtual void f1() = 0;
...
virtual void f10() = 0;
template<typename T>
OStream& operator<&...
- 49
3
votes
1
answer
2k
views
Producing a library with a recent gcc and consuming it with an older gcc - Why are there issues despite the same C++ version?
Don't ask me why I am doing what I am doing... that would be a long story.
For now, the purpose of this post is to learn and to understand why things don't work the way I expect. Possibly my ...
- 167
0
votes
2
answers
531
views
std::unordered_map ordering change while traversing during different executions
Suppose there is class Heavy with a bunch of user-defined compound class members. One of that, let's name it m_hashMap, has std::unordered_map<unsigned int, std::vector<CompoundClass>> ...
- 49
3
votes
1
answer
178
views
Program works on GCC 7.5 on PC but not on online compiler
I have the following program that compiles successfully on my machine using GCC 7.5.0 but when i try out the program here the program doesn't work.
class Foo
{
friend void ::error() { }
};
int ...
1
vote
0
answers
922
views
QNX7 and GCC 5.4.0 and CMAKE (fatal error: map: No such file or directory compilation terminated.)
I use CMAKE to cross compile my code for QNX6.5 and using gcc/g++ 4.4.2
I added a new tool chain file for QNX7 using gcc/g++ 5.4.0. My issue is that I am failing the build on standard includes like ...
0
votes
0
answers
42
views
error: cannot bind non-const lvalue reference of type ** to an rvalue of type ** [duplicate]
I am working on compiling some old api code that was written back in mid to late 90's, it is written in C++98 and I am using GCC on linux.
I have this line of offending code:
UnpackCommunityData(data....
- 13
1
vote
0
answers
494
views
gcc and clang: thread library is successfully included but nothing won't be compiled with that
I've got specific error that I haven't encountered before.
Before I'll start, I need to say that I work on a server and have no root rights. /usr/bin and /usr/local/bin are missing many packages and ...
- 41
3
votes
1
answer
922
views
VSCode C++ Debugger Mac not Linking CPP files
I am trying to run the debugger for a simple "hello world" like program but am running into linking errors.
I only have 3 files, Log.h, Log.cpp, Main.cpp:
Log.h
#pragma once
void InitLog();
...
- 321
-1
votes
1
answer
58
views
C++11 is not executing switch correctly when variable is declared in case block
Consider the snippet below. If I compile this with GCC/C++11 then I expect that if I call this with e.g. var=2 that that block is executed. Anyway I expect at least one of the 3 switch blocks are ...
- 2,027
1
vote
3
answers
420
views
Replace C++ class/static method with preprocessor?
I'd like to use the built-in compiler checks to verify format strings of a custom logging framework to catch the odd runtime crash due to mismatching format string <-> parameters in advance.
...
- 4,486
1
vote
1
answer
131
views
Why is my exception sliced to base class if I catch it with reference to base class?
So I've written a small C++ class as follows:
class bad_hmean : public std::logic_error {
const char *nature_;
char *what_;
public:
bad_hmean(const char *fname);
~bad_hmean() { ...
0
votes
1
answer
62
views
Why does std::regex_match generate different results
I'm trying to use std::regex to validate some variables from a file in my c++11 project.
For now I need to validate if a string is a valid URL or not. Here is my code: https://godbolt.org/z/4Pn9eYEce
...
- 12.2k
2
votes
1
answer
343
views
g++ compiler gives me errors with -std=c++11 flag, but it compiles fine with -std=gnu++11. what does this mean?
I'm maintaining an old server at work, which is running on CentOS6(gcc (GCC) 4.4.7, C++98)
and I was trying to migrate it to CentOS7(gcc (GCC) 4.8.5) with C++11.
At first, I tried to compile with a ...
- 31