C / C++ / MFC Discussion Boards

Re: Create a Makefile from this mess

pkfox8-Oct-22 5:42

pkfox

8-Oct-22 5:42

Thanks Richard that will certainly get me started, what does -o $@ set the output file to ?

Life should not be a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming “Wow! What a Ride!" - Hunter S Thompson - RIP

Re: Create a Makefile from this mess

Richard MacCutchan8-Oct-22 5:57

Richard MacCutchan

8-Oct-22 5:57

The $@ is one of the predefined make macros and refers to the target of the build; which should be the output file callapi. I looked at the man page for make on Ubuntu but it seems incomplete. There is (certainly used to be) a section somewhere that gives all the details on Makefile structures.

Re: Create a Makefile from this mess

pkfox8-Oct-22 6:17

pkfox

8-Oct-22 6:17

With your help I've cobbled this together ( and it works Big Grin | :-D

) thanks again

INCS = -I /home/pjk/C++/CallCommandsAPI/Headers/ \
       -I /home/pjk/vcpkg/packages/rapidjson_x64-linux/include/ \
       -I /home/pjk/vcpkg/packages/cpr_x64-linux/include/

LIBS = -L /home/pjk/vcpkg/packages/cpr_x64-linux/lib/ \
       -lcpr -lcurl -lpthread -lssl -lcrypto 

SOURCES = $(wildcard *.cpp */*.cpp)

TARGET: callapi

callapi: $(SOURCES)
    g++ $(SOURCES) -o $@ $(INCS) $(LIBS)

clean:
    rm callapi

Re: Create a Makefile from this mess

k505413-Oct-22 5:53

k5054

13-Oct-22 5:53

If you are interested in using the power of make to only compile modified sources that are newer than the target you should be able to do something like this

CPPFLAGS = -I /home/pjk/vcpkg/packages/cpr_x64-linux/include/cpr \
    -I /home/pjk/C++/CallCommandsAPI/Headers/ \
    -I /home/pjk/vcpkg/packages/rapidjson_x64-linux/include/ \
    -I /home/pjk/vcpkg/packages/cpr_x64-linux/include/

LDFLAGS = -L /home/pjk/vcpkg/packages/cpr_x64-linux/lib/ \
    -lcpr -lcurl -lpthread -lssl -lcrypto

SRCS = $(wildcard Source/*.cpp)
OBJS = $(SRCS:.cpp=.o)

ifdef DEBUG
   CXXFLAGS += -ggdb
   LDFLAGS += -ggdb
else
   CXXFLAGS += -O2
   LDFLAGS += -O2
endif

callapi: $(OBJS)
        $(CXX) $(LDFLAGS) $^ -o $@

clean:
        rm -f callapi $(OBJS)

I've added clean and debug options to help maintain your code. To make a debug version you do

Shell

make DEBUG=1

Note that $CPPFLAGS and $CXXFLAGS are standard make variables and will be expanded when trying to compile the individual object files, without us having to explicitly tell make to do so.
If you don't want the object files mixed in the source directory, look into using $(patsubst) [Text Functions (GNU make)](https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#Text-Functions) and/or other make functions to manipulate targets. With some fancy footwork you could also get debug and production objects built at the same time, but I'll leave that as an exercise for the reader!

Keep Calm and Carry On

Re: Create a Makefile from this mess

pkfox13-Oct-22 21:40

pkfox

13-Oct-22 21:40

Thanks for this, one question, where is CXX defined ?

Re: Create a Makefile from this mess

k505414-Oct-22 4:13

k5054

14-Oct-22 4:13

CXX is defined in the bowels of make somewhere. It is the default variable for the C++ compiler, and is used in the rules for constructing default recipes. So for example, suppose you had an otherwise empty directory with only one file, hello.cpp, in it. Without needing to create a Makefile, you can build the hello executable just by saying "make hello". There's default rules for all kinds of things, C, Fortran, ranlib (.a) libraries, yacc, tex, and on and on. You can get a list of available recipes by saying "make -p", which for my version of make produces 1357 lines of output.

The CXX variable can be overridden by specifiying a shell variable of the same name at run time, so if for example you wanted to see what error messages clang++ spits out instead of g++ you can say

Bash

CXX=clang++ make target

Similarly you have CXXFLAGS and CPPFLAGS which pass arguments to the C++ compiler and the CPreProcessor, respectively. So you could say

Bash

CXX=clang++ CPPFLAGS="-I /path/to/includs" CXXFLAGS="-O2 -Wall -Wextra" LDFLAGS="-L /path/to/lib" LDLIBS="-lmylib1 -lmylib2" make hello

and make will apply the variables to the generated command line as expected, and produce:

clang++ -O2 -Wall -Wextra -I /path/to/includs -L /path/to/lib  hello.cc  -lmylib1 -lmylib2 -o hello

gnu make hack: You can rebuild everything from scratch, even if already compiled, without having to "make clean" by using the -B flag

It should also be noted that the Makefile I provided earlier uses GNU makeisms e.g. $(wildcard),$(patsubst). If you find yourself on a BSD or other unix like system that does not have GNU tools installed, the given make file will fail. But the variable substitutions mentioned here will still work.

Keep Calm and Carry On

Is this array of 2D vectors?

Sk. Azraf Sami7-Oct-22 20:32

Sk. Azraf Sami

7-Oct-22 20:32

C++

vector<vector<int>> mark[5]

Is this array of 2D vectors? How can I traverse or insert any element from user in this data structure?

Re: Is this array of 2D vectors?

Richard MacCutchan7-Oct-22 21:35

Richard MacCutchan

7-Oct-22 21:35

Try breaking it down into its constituent parts:

mark is an array of 5 elements.
Each element is a vector.
And each element of the vector is also a vector.
And each element of the inner vectors is an integer.

As it stands though, the array is null, so you need to initialise each of its elements with a new vector. You then need to decide what actual information you want to store in the vectors.

Style question

Mircea Neacsu3-Oct-22 15:33

Mircea Neacsu

3-Oct-22 15:33

I have a C++ function that takes as argument an iterator and needs to increment it without passing the end of the container. I can write it as:
variant A:

C++

bool func (std::string::iterator& ptr, std::string& container)
{
  //...
  if (ptr != container.end())
    //do stuff
}

and call it as:

C++

func (s.begin(), s);

or I could write it as
variant B:

C++

bool func (std::string::interator& ptr, std::string::const_iterator& limit)
{
  //...
  if (ptr != limit)
    //do stuff
}

and call it as:

C++

func (s.begin(), s.end());

(the example assumes the container is a string but that's not important)

Which one would you favor?

Mircea

Re: Style question

Graham Breach3-Oct-22 21:23

Graham Breach

3-Oct-22 21:23

If the function modified the contents of the container I would probably pass it the container reference, otherwise I would prefer the iterators (or even a std::span).

Re: Style question

Mircea Neacsu4-Oct-22 2:27

Mircea Neacsu

4-Oct-22 2:27

Good points, thank you! However std::span is C++20 and I want to keep the code C++14.

Mircea

Re: Style question

CPallini3-Oct-22 23:47

CPallini

3-Oct-22 23:47

The second one: give to the function the strict necessary for its task.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Re: Style question

Mircea Neacsu4-Oct-22 2:28

Mircea Neacsu

4-Oct-22 2:28

Yep, my thoughts exactly. Thank you!

Mircea

Re: Style question

CPallini7-Oct-22 1:35

CPallini

7-Oct-22 1:35

"great minds..."
Laugh | :laugh:

You are welcome.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Re: Style question

BernardIE53177-Oct-22 3:14

BernardIE5317

7-Oct-22 3:14

I have a more or less strict rule i.e. to wit in particular to be specific namely things that act like pointers are passed via copy constructor not via reference since raw pointers are fundamental type objects so take up little space and a reference is a pointer anyway. I agree w/ the chap who suggested passing only what the function requires i.e. first, last iterators. Further at point of call the code is easier to understand its purpose as it passes only what the function requires also it just looks better and is easier to understand as fewer ideas/concepts are involved namely the one idea/concept "iterator" rather than the two ideas/concepts "iterator and container". Was there not a recent article in a recent CP newsletter discussing this very thing i.e. minimizing the number of ideas/concepts needed to understand any code?

Re: Style question

Mircea Neacsu7-Oct-22 3:18

Mircea Neacsu

7-Oct-22 3:18

meagreProgrammer wrote:
things that act like pointers are passed via copy constructor not via reference

Except that in my case the iterator needs to be changed by the function, hence I have to pass a reference.

Mircea

Re: Style question

BernardIE53177-Oct-22 3:27

BernardIE5317

7-Oct-22 3:27

Would it be too lengthy or tedious an explanation to explain the need to modify the iterator. I find such a need quite unusual and do not recall ever having to perform same.

Re: Style question

Mircea Neacsu7-Oct-22 3:40

Mircea Neacsu

7-Oct-22 3:40

No problem: the iterator is a pointer in a UTF-8 encoded string and the function (called next) has to advance to the next code point (1, 2, 3 or 4 char). If iterator is at end of string it doesn't advance.

Although a very simple function, I had a number of design decisions to make:
- How should I deal with improperly encoded UTF-8 strings? I decided to return false if the string is not properly encoded.
- Should I just leave out the boundary check and just document it? I decided against as it would have been unsafe.

And the last one I was asking about: For limit check, should I just pass the string or the end iterator.

Mircea

'System': a namespace with this name does not exist

Kevin Marois3-Oct-22 6:12

Kevin Marois

3-Oct-22 6:12

I am NOT a C++ guy, so bear with me.

I am working on a C#/WPF app that references two C++ projects.

We just converted the solution from .Net Framework to .Net Core 6.0, and now the C++ projects won't compile while in the solution. If I open the C++ projects stand-alone, they compile file.

Primarily I'm getting the compile time error

'System': a namespace with this name does not exist

I've been Googling and 99% of the answers all say this. I've tried the answers and still get the same errors.

At this point I need help. I'm guessing it's some kind of configuration issue, but I really don't know.

Thanks

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Re: 'System': a namespace with this name does not exist

Richard MacCutchan3-Oct-22 6:26

Richard MacCutchan

3-Oct-22 6:26

An error message by itself does not tell us much. What is the context, and are you sure this would not fit better in Managed C++/CLI Discussion Boards[^] ?

Re: 'System': a namespace with this name does not exist

Kevin Marois3-Oct-22 6:30

Kevin Marois

3-Oct-22 6:30

Richard MacCutchan wrote:
What is the context

Not sure what you mean by "what is the context". Like I said, the project is in a solution with a C#/WPF project and the C++ project now doesn't compile.

Richard MacCutchan wrote:
and are you sure this would not fit better in Managed C++/CLI Discussion Boards

I have no clue. But I could move it there.

Again, I have ZERO C++ experience, so I'm really in the dark with all this.

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Re: 'System': a namespace with this name does not exist

Richard MacCutchan3-Oct-22 6:39

Richard MacCutchan

3-Oct-22 6:39

Kevin Marois wrote:
Not sure what you mean by "what is the context"

All you have given us is an error message. We have no idea whether this is unmanaged or managed code, what the actual code that causes the error looks like &c.

Re: 'System': a namespace with this name does not exist

Kevin Marois3-Oct-22 6:43

Kevin Marois

3-Oct-22 6:43

OK, so here's the lines of code that are failing:

using namespace System;
using namespace System::Reflection;
using namespace System::Runtime::CompilerServices;
using namespace System::Runtime::InteropServices;
using namespace System::Security::Permissions;

This error occurs in the using statements in every C++ file in the project.

It's a .Net 6 project, so I'm assuming it Managed code.

I'm not trying to be difficult, but I just don't know what I'm looking at so it's hard for me to know what to post here.

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

Re: 'System': a namespace with this name does not exist

Richard MacCutchan3-Oct-22 6:50

Richard MacCutchan

3-Oct-22 6:50

OK, what you have is managed C++, AKA C++/CLI, which uses .NET. Those using statements are correct and it should build. However since you are converting from the Net Framework you probably need to look at Migrating C++/CLI projects to .NET Core and .NET 5+ - .NET Core | Microsoft Learn[^].

Re: 'System': a namespace with this name does not exist

Kevin Marois3-Oct-22 6:51

Kevin Marois

3-Oct-22 6:51

OK thanks. I'll take a look

If it's not broken, fix it until it is.
Everything makes sense in someone's mind.
Ya can't fix stupid.

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