Building multiple binaries within one Eclipse project - c++

How can I get Eclipse to build many binaries at a time within one project (without writing a Makefile by hand)?
I have a CGI project that results in multiple .cgi programs to be run by the web server, plus several libraries used by them. The hand-made Makefile used to build it slowly becomes unmaintainable. We use Eclipse's "Internal Build" to build all other projects and we'd prefer to use it here too, but for the good of me, I can't find how to get Eclipse to build multiple small programs as result instead of linking everything into one binary.

Solution for this described there: http://tinyguides.blogspot.ru/2013/04/multiple-binaries-in-single-eclipse-cdt.html.
There is an excerpt:
Create a managed project (File > New C++ Project > Executable)
Add the source code containing multiple main() functions
Go to Project > Properties > C/C++ General > Path & Symbols > Manage Configurations
Make a build configuration for each executable and name it appropriately (you can clone existing configurations like Debug and Release).
From the project explorer, right click on each source file that contains a main() function > Resource Configurations > Exclude from Build and exclude all build configurations except the one that builds the executable with this main() function
All other code is included in all build configurations by default. You may need to change this depending on your application.
You can now build an executable for each main function by going to Project > Build Configurations > Set Active , Project > Build Project

Using Eclipse as your build system for production code seems like a bad idea in general. I think it's a great IDE and have used it extensively for both Java and C++ projects, but for a build system I firmly believe that Ant, make, and other dedicated build utilities are the way to go.
There are several reasons for this:
Dedicated build utilities offer the very flexibility you are looking for in generating multiple executable targets.
Ant and make support most conceivable arbitrary build process chains (though not quite all).
A dedicated build utility is likely to offer greater stability and backward-compatibility for build description file formats than an IDE tool like Eclipse. Also, I'm pretty sure that Eclipse's internal build feature is dependent on the ".project" file description, and the latter's format is probably not as stable as the build description format for either Ant or make.
General-purpose, basic build utilities are usually command-line-based, which makes it easy to integrate them with more sophisticated, higher-level build utilities for automated build management like Pulse, CruiseControl, etc.
The need that is motivating your question is telling you that it's time to make the switch to a better build tool.

There is a way to use buildconfigurations to create one binary (or shared library, in my case) from each build config. Using the answer above, this means to manually exclude all but the effective main file from each build config.
I just used the above answers to ease up working on my eclipse project that creates 14 shared libraries through 14 build configs. However, configuring the indivdual "exclude from build" setting was quite cumbersome, so I switched to using the following code relying on a preprocessor-directive as my complete main file:
/*
*main.cpp
*/
/* Within
* Project | Properties | C/C++-Build | Settings
* | GCC C++ Compiler | Preprocessor
* set the following defined Symbol:
* _FILENAME=${ConfigName}
*/
#define __QUOT2__(x) #x
#define __QUOT1__(x) __QUOT2__(x)
#include __QUOT1__(_FILENAME.cpp)
#undef __QUOT1__
#undef __QUOT2__
/* The above include directive will include the file ${CfgName}.cpp,
* wherein ${CfgName} is the name of the build configuration currently
* active in the project.
*
* When right clicking in
* Project Tree | (Project)
* and selecting
* Build Configuration | Build all
* this file will include the corresponding .cpp file named after the
* build config and thereby effectively take that file as a main file.
*
* Remember to exclude ALL ${CfgName}.cpp files from ALL build configurations.
*/
Note that it does nothing else then include another .cpp file which's name is deduced from the preprocessor and a symbol that is set in the compiler options. The symbol is ${CfgName} and will be replaced by the current config name by eclipse automatically.
One does not need to configure, which file is included in which build config. Just exclude all ${CfgName}.cpp files in every build and include main.cpp in every build.
PS: the answer from hovercraft gave me the idea to have a main file that does not contain code on its own. If one includes shared code from the different effective main files ${CfgName}.cpp, working on their code may become infeasible because header files in main.cpp will not be visible in them.
I did this until yesterday, but maintaining the code with broken index etc. was a big pain.
PPS: this procedure currently breaks the automatic rebuild of the main file if only the included .cpp file was changed. It seems that eclipse does not recognize the changes in ${CfgName}.cpp (which is excluded from build). So a manual rebuild is required after every change. This is currently bugging me ;)

Related

How to exclude source files by configuration in CLion?

As shown below, Threre are two directories that are exclusively included in the build depending on the build option. (by setting CMake)
ROOT
-- src
-- moduleA
-- codeA.c
-- moduleB
-- codeB.c
commonCode.c
funcSameNameDifferentImpl function exist in both codeA.c and codeB.c. It is used in commonCode.c
In this case, how I exclude codeA.c from CLion source control indexing? When I try to navigate or go to definition, IDE is NOT working as I expected. Even IDE bring me to source file excluded in build with kind warning 'This file does not belong to any project...'
I found out below guide and check overriding file type as plain text is working well. But, I think it is too ugly, not elegant.
https://www.jetbrains.com/help/clion/controlling-source-library-and-exclude-directories.html
Is there a nice way to exclude files and directories from CLion indexing?
I think it's intuitive behavior for indexing to change automatically depending on the build target.

Out of source builds (external build directory) with Cargo?

Having used CMake, I've become used to out-of-source builds, which are encouraged with CMake. How can out-of-source builds be done with Cargo?
Using in-source-builds again feels like a step backwards:
Development tools need to be configured to ignore paths. Sometimes multiple plugins and development tools - especially using VIM or Emacs!
Some tools can't be configured to easily hide build files. While dotfiles are typically hidden, they will still show Cargo.lock and target/, worse still, recursively exposing their contents.
Deleting un-tracked files to remove everything outside of version control, typically to cleanup editor temp files or some test output, can backfire if you forgot to add a new file to version control and don't manually check the file list properly before deleting them.
Dependencies are downloaded into your source code path, sometimes adding *.rs files in the target directory as part of building indirect deps, so operating on all *.rs files may accidentally pickup other files which aren't in a hidden directory, so might not be ignored even after development tools have been configured.
While it's possible to work around all these issues, I'd rather just have an external build path and keep the source directory pristine.
You can specify the directory of the target/ folder either via configuration file (key build.target-dir) or environment variable (CARGO_TARGET_DIR). Here is an example using a configuration file:
Suppose you want to have a directory ~/work/ in which you want to save the Cargo project (~/work/foo/) and next to it the target directory (~/work/my-target/).
$ cd ~/work
$ cargo new --bin foo
$ mkdir .cargo
$ $EDITOR .cargo/config
Then insert the following into the configuration file:
[build]
target-dir = "./my-target"
If you then build in your normal Cargo project directory:
$ cd foo
$ cargo build
You will notice that there is no target/ dir, but everything is in ~/work/my-target/.
However, the Cargo.lock is still saved inside the Cargo project directory, but that kinda makes sense. For executables, you should check the Cargo.lock file into your git! For libraries, you shouldn't. I guess having to ignore one file is better than having to ignore an entire folder.
Lastly, there are a few caveats to changing the target-dir, which are listed in the PR which introduced the feature.
While useful manually setting this up isn't all that convenient, I wanted to be able to build multiple crates within a source tree, having all of them out-of-source, something that ../target-dir configuration option wouldn't achieve.
Helper utility for convenient out-of-source builds
Using the environment variable I've written a small utility to wrap cargo, so it automatically builds out-of-source, supporting crates both at the top-level, on in a subdirectory of the source tree.
Thanks to Lukas for pointing out CARGO_TARGET_DIR and target-dir configuration option.
What I really wanted was a dynamic CARGO_TARGET_DIR that changes relative to where I am.
This bash alias puts all builds in a mirrored directory structure, e.g. instead of putting target into ~/mydir/myproj it puts in into ~/rustbuild/mydir/myproj
alias cargo='CARGO_TARGET_DIR=$(echo $PWD | sed "s|$HOME|$HOME/rustbuild|g") cargo'
You could also make your rustbuild directory hidden.

waf: nested projects and _cache.py: not supported?

I am converting a project from autotools to waf with the hope that it can be easily compiled in windows as well.
I am using a super project with two children folders that are 2 projects.
One of them is a library, the other, a program, like this:
superproject/wscript
superproject/libraryproject/wscript
superproject/programproject/wscript
It seems that waf has terrible support for subprojects. I have a wscript in each of these directories.
I recurse from superproject into the 2 other projects, but the _cache.py file is shared for both projects. This has the following side effects (issues):
When using the boost tool, I had to use it like this to avoid name collisions:
# In library project
cfg.check_boost('boost_program_options', uselib_store='BOOST_LIBRARYPROJECT')
# In program project
cfg.check_boost('boost_program_options', uselib_store='BOOST_PROGRAMPROJECT')
boost-libs and boost-includes command line options are also lost by default, so I have to set them manually, like this:
cfg.env.LIBPATH_BOOST_PROGRAMPROJECT = cfg.options.boost_libs
...
The _cache.py file is overwritten by the programproject/wscript, loosing all the configuration for the flags.
Questions:
Is there any good way to nest projects and avoid at least issue 2?
Is there any reasonable way to avoid both that doesn't require a script and building projects separately?
Configuration file is not written twice.
My mistake was to do this:
cfg.env = ConfigSet()
I wanted a new and clean ConfigSet but doing that in both projects made the first set of flags to be lost.
Since the environment seems to be shared among all project configurations, is it good style to name the variables with custom names? For example, instead of using:
cfg.check_boost('program_options')
Should I use:
cfg.check_boost('program_options', uselib_store='BOOST_MYPROGRAMPROJECT')
Is this good style or it's usually done in another way?
Can be done in a cleaner way deriving ConfigSets?

How to get a python .pyd for Windows from c/c++ source code? (update: brisk now in Python in case that's what you want)

How to get from C/C++ extension source code to a pyd file for windows (or other item that I could import to Python)?
edit: The specific library that I wanted to use (BRISK) was included in OpenCV 2.4.3 so my need for this skill went away for the time being. In case you came here looking for BRISK, here is a simple BRISK in Python demo that I posted.
I have the Brisk source code (download) that I would like to build and use in my python application. I got as far as generating a brisk.pyd file... but it was 0 bytes. If there is a better / alternative way to aiming for a brisk.pyd file, then of course I am open to that as well.
edit: Please ignore all the attempts in my original question below and see my answer which was made possible by obmarg's detailed walkthrough
Where am I going wrong?
Distutils without library path: First I tried to build the source as is with distutils and the following setup.py (I have just started learning distutils so this is a shot in the dark). The structure of the BRISK source code is at the bottom of this question for reference.
from distutils.core import setup, Extension
module1 = Extension('brisk',
include_dirs = ['include', 'C:/opencv2.4/build/include', 'C:/brisk/thirdparty/agast/include'],
#libraries = ['agast_static', 'brisk_static'],
#library_dirs = ['win32/lib'],
sources = ['src/brisk.cpp'])
setup (name = 'BriskPackage',
ext_modules = [module1])
That instantly gave me the following lines and a 0 byte brisk.pyd somewhere in the build folder. So close?
running build
running build_ext
Distutils with library path: Scratch that attempt. So I added the two library lines that are commented out in the above setup.py. That seemed to go ok until I got this linking error:
creating build\lib.win32-2.7
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\BIN\link.exe /DLL /nologo /INCREMENTAL:NO /LIBPATH:win32/lib /LIB
PATH:C:\Python27_32bit\libs /LIBPATH:C:\Python27_32bit\PCbuild agast_static.lib brisk_static.lib /EXPORT:initbrisk build
\temp.win32-2.7\Release\src/brisk.obj /OUT:build\lib.win32-2.7\brisk.pyd /IMPLIB:build\temp.win32-2.7\Release\src\brisk.
lib /MANIFESTFILE:build\temp.win32-2.7\Release\src\brisk.pyd.manifest
LINK : error LNK2001: unresolved external symbol initbrisk
build\temp.win32-2.7\Release\src\brisk.lib : fatal error LNK1120: 1 unresolved externals
error: command '"C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\BIN\link.exe"' failed with exit status 1120
Uncontrolled flailing: I thought maybe the libraries needed to be built, so I did a crash course (lots of crashing) with cmake + mingw - mingw + vc++ express 2010 as follows:
cmake gui: source: c:/brisk, build: c:/brisk/build
cmake gui: configure for Visual Studio 10
cmake gui: use default options and generate (CMAKE_BACKWARDS_COMPATIBILITY, CMAKE_INSTALL_PREFIX, EXECUTABLE_OUTPUT_PATH, LIBRARY_OUTPUT_PATH)
VC++ Express 10: Change to Release and build the solution generated by cmake and get about 20 pages of what look like non-critical warnings followed by all succeeded. Note - no dlls are generated by this. It does generate the following libraries of similar size to the ones included with the download:
win32/lib/Release/
agast_static.lib
brisk_static.lib
Further flailing.
Relevant BRISK source file structure for reference:
build/ (empty)
include/brisk/
brisk.h
hammingsse.hpp
src
brisk.cpp
demo.cpp
thirdparty/agast/
include/agast/
agast5_8.h ....
cvWrapper.h
src/
agast5_8.cc ...
CMakeLists.txt
win32/
bin/
brisk.mexw32
opencv_calib3d220.dll ...
lib/
agast_static.lib
brisk_static.lib
CMakeLists.txt
FindOpenCV.cmake
Makefile
Are you sure that this brisk library even exports python bindings? I can't see any reference to it in the source code - it doesn't even seem to import python header files. This would certainly explain why you've not had much success so far - you can't just compile plain C++ code and expect python to interface with it.
I think your second distutils example is closest to correct - it's obviously compiling things and getting to the linker stage, but then you encounter this error. That error just means it can't find a function named initbrisk which I'm guessing would be the top level init function for the module. Again this suggests that you're trying to compile a python module from code that isn't meant for it.
If you want to wrap the C++ code in a python wrapper yourself you could have a look at the official documentation on writing c/c++ extensions. Alternatively you could have a look into boost::python, SIP or shiboken which try to somewhat (or completely) automate the process of making python extensions from C++ code.
EDIT: Since you seem to have made a decent amount of effort to solve the problem yourself and have posted a good question, I've decided to give a more detailed response on how to go about doing this.
Quick Tutorial On Wrapping C++ Libraries Using boost::python
Personally I've only ever used boost::python for stuff like this, so I'll try and give you a good summary of how to go about doing that. I'm going to assume that you're using Visual C++ 2010. I'm also going to assume that you've got a 32bit version of python installed, as I believe the boost pro libraries only provide 32bit binaries.
Installing boost
First you'll need to grab a copy of the boost library. The easiest way to do this is to download an installer from the boost pro website. These should install all the header files and binary files that are required for using the boost c++ library on windows. Take note of where you install these files to, as you'll need them later on - it might be best to install to a path without a space in it. For easyness I'm going to assume you put these files in C:\boost but you can substitute that for the path you actually used.
Alternatively, you can follow these instructions to build boost from source. I'm not 100% sure, but it might be the case that you need to do this in order to get a version of boost::python that is compatible with the version of python you have installed.
Setting up a visual studio project
Next, you'll want to setup a visual studio project for brisk.pyd. If you open visual studio, go to New -> Project then find the option for Win32 Project. Set up your location etc. and click ok. In the wizard that appears select a DLL project type, and then tick the empty project checkbox.
Now that you've created your project, you'll need to set up the include & library paths to allow you to use python, boost::python and the brisk.lib file.
In Visual Studios solution explorer, right click on your project, and select properties from the menu that appears. This should open up the property pages for your project. Go to the Linker -> General section and look for the Additional Library Directories section. You'll need to fill this in with the paths to the .lib files for boost, python and your brisk_static.lib. Generally these can be found in lib (or libs) subdirectories of
wherever you've installed the libraries. Paths are seperated with semicolons. I've attached a screenshot of my settings below:
Next, you'll need to get visual studio to link to the .lib files. These sections can be found in the Additional Dependencies field of the Linker -> Input section of the properties. Again it's a semicolon delimited list. You should need to add in libraries for python (in my case this is python27.lib but this will vary by version) and brisk_static.lib. These do not require the full path as you added that in the previous stage. Again, here's a screenshot:
You may also need to add the boost_python library file but I think boost uses some header file magic to save you the trouble. If I'm incorrect then have a look in you boost library path for a file named similar to boost_python-vc100-mt.lib and add that in.
Finally, you'll need to setup the include paths to allow your project to include the relevant C++ header files. To get the relevant settings to appear in project properties, you'll need to add a .cpp file to your project. Right click the source files folder in your solution explorer, and then go to add new item. Select a C++ File (.cpp) and name it main.cpp (or whatever else you want).
Next, go back to your project properties and go to C/C++ -> General. Under the additional libraries directory you need to add the include paths for brisk, python and boost. Again, semicolons for seperators, and again here's a screenshot:
I suspect that you might need to update these settings to include the opencv2 & agast libraries as well but I'll leave that as a task for you to figure out - it should be much the same process.
Wrapping existing c++ classes with boost::python.
Now comes the slightly trickier bit - actually writing C++ to wrap your brisk library in boost python. You can find a tutorial for this here but i'll try and go over it a bit as well.
This will be taking place in the main.cpp file you created earlier. First, add the relevant include statements you'll need at the top of the file:
#include <brisk/brisk.h>
#include <Python.h>
#include <boost/python.hpp>
Next, you'll need to declare your python module. I'm assuming you'd want this to be called brisk, so you do something like this:
BOOST_PYTHON_MODULE(brisk)
{
}
This should tell boost::python to create a python module named brisk.
Next it's just a case of going through all the classes & structs that you want to wrap and declaring boost python classes with them. The declerations of the classes should all be contained in brisk.h. You should only wrap the public members of a class, not any protected or private members. As a quick example, I've done a couple of the structs here:
BOOST_PYTHON_MODULE(brisk)
{
using namespace boost::python;
class_< cv::BriskPatternPoint >( "BriskPatternPoint" )
.def_readwrite("x", &cv::BriskPatternPoint::x)
.def_readwrite("y", &cv::BriskPatternPoint::y)
.def_readwrite("sigma", &cv::BriskPatternPoint::sigma);
class< cv::BriskScaleSpace >( "BriskScaleSpace", init< uint8_t >() )
.def( "constructPyramid", &cv::BriskScaleSpace::constructPyramid );
}
Here I have wrapped the cv::BriskPatternPoint structure and the cv::BriskScaleSpace class. Some quick explanations:
class_< cv::BriskPatternPoint >( "BriskPatternPoint" ) tells boost::python to declare a class, using the cv::BriskPatternPoint C++ class, and expose it as BriskPatternPoint in python.
.def_readwrite("y", &cv::BriskPatternPoint::y) adds a readable & writeable property to the BriskPatternPoint class. The property is named y, and will map to the BriskPatternPoint::y c++ field.
class< cv::BriskScaleSpace >( "BriskScaleSpace", init< uint8_t >() ) declares another class, this time BriskScaleSpace but also provides a constructor that accepts a uint8_t (an unsigned byte - which should just map to an integer in python, but I'd be careful to not pass in one greater than 255 bytes - I don't know what would happen in that situation)
The following .def line just declares a function - boost::python should (I think) be able to determine the argument types of functions automatically, so you don't need to provide them.
It's probably worth noting that I haven't actually compiled any of these examples - they might well not work at all.
Anyway, to get this fully working in python it should just be a case of doing similar for every structure, class, property & function that you want accessible from python - which is potentially quite a time consuming task!
If you want to see another example of this in action, I did this here to wrap up this class
Building & using the extension
Visual studio should take care of building the extension - then using it is just a case of taking the .DLL and renaming it to .pyd (you can get VS to do this for you, but I'll leave that up to you).
Then you just need to copy your python file to somewhere on your python path (site-packages for example), import it and use it!
import brisk
patternPoint = brisk.BriskPatternPoint()
....
Anyway, I have spent a good hour or so writing this out - so I'm going to stop here. Apologies if I've left anything out or if anything isn't clear, but I'm doing this mostly from memory. Hopefully it's been of some help to you. If you need anything clarified please just leave a comment, or ask another question.
In case someone needs it, this what I have so far. Basically a BriskFeatureDetector that can be created in Python and then have detect called. Most of this is just confirming/copying what obmarg showed me, but I have added the details that get all the way to the pyd library.
The detect method is still incomplete for me though since it does not convert data types. Anyone who knows a good way to improve this, please do! I did find, for example, this library which seems to convert a numpy ndarray to a cv::Mat, but I don't have the time to figure out how to integrate it now. There are also other data types that need to be converted.
Install OpenCV 2.2
for the setup below, I installed to C:\opencv2.2
Something about the API or implementation has changed by version 2.4 that gave me problems (maybe the new Algorithm object?) so I stuck with 2.2 which BRISK was developed with.
Install Boost with Boost Python
for the setup below, I installed to C:\boost\boost_1_47
Create a Visual Studio 10 Project:
new project --> win32
for the setup below, I named it brisk
next --> DLL application type; empty project --> finished
at the top, change from Debug Win32 to Release Win32
Create main.cpp in Source Files
Do this before the project settings so the C++ options become available in the project settings
#include <boost/python.hpp>
#include <opencv2/opencv.hpp>
#include <brisk/brisk.h>
BOOST_PYTHON_MODULE(brisk)
{
using namespace boost::python;
//this long mess is the only way I could get the overloaded signatures to be accepted
void (cv::BriskFeatureDetector::*detect_1)(const cv::Mat&,
std::vector<cv::KeyPoint, std::allocator<cv::KeyPoint>>&,
const cv::Mat&) const
= &cv::BriskFeatureDetector::detect;
void (cv::BriskFeatureDetector::*detect_vector)(const std::vector<cv::Mat, std::allocator<cv::Mat>>&,
std::vector< std::vector< cv::KeyPoint, std::allocator<cv::KeyPoint>>, std::allocator< std::vector<cv::KeyPoint, std::allocator<cv::KeyPoint>>>>&,
const std::vector<cv::Mat, std::allocator<cv::Mat>>&) const
= &cv::BriskFeatureDetector::detect;
class_< cv::BriskFeatureDetector >( "BriskFeatureDetector", init<int, int>())
.def( "detect", detect_1)
;
}
Project Settings (right-click on the project --> properties):
Includes / Headers
Configuration Properties --> C/C++ --> General
add to Additional Include Directories (adjust to your own python / brisk / etc. base paths):
C:\opencv2.2\include;
C:\boost\boost_1_47;
C:\brisk\include;C:\brisk\thirdparty\agast\include;
C:\python27\include;
Libraries (linker)
Configuration Properties --> Linker --> General
add to Additional Library Directories (adjust to your own python / brisk / etc. base paths):
C:\opencv2.2\lib;
C:\boost\boost_1_47\lib;
C:\brisk\win32\lib;
C:\python27\Libs;
Configuration Properties --> Linker --> Input
add to Additional Dependencies (adjust to your own python / brisk / etc. base paths):
opencv_imgproc220.lib;opencv_core220.lib;opencv_features2d220.lib;
agast_static.lib; brisk_static.lib;
python27.lib;
.pyd output instead of .dll
Configuration Properties --> General
change Target Extension to .pyd
Build and rename if necessary
Right-click on the solution and build/rebuild
you may need to rename the output from "Brisk.pyd" to "brisk.pyd" or else python will give you errors about not being able to load the DLL
Make brisk.pyd available to python by putting it in site packages or by putting a .pth file that links to its path
Update Path environment variable
In windows settings, make sure the following are included in your path (again, adjust to your paths):
`C:\boost\boost_1_47\lib;C:\brisk\win32\bin`

Compiling C++Builder project on command line

Is there a way to compile a C++Builder project (a specific build configuration) from the command line?
Something like:
CommandToBuild ProjectNameToBuild BuildConfiguration ...
There are different ways for automating your builds in C++Builder (as of my experience, I'm speaking about old C++Builder versions like 5 and 6).
You can manually call compilers - bcc32.exe (also dcc32.exe, brcc32.exe and tasm32.exe if you have to compile Delphi units, resource files or assembly language lines of code in your sources) and linker - ilink32.exe.
In this case, you will need to manually provide the necessary input files, paths, and keys as arguments for each stage of compilation and linking.
All data necessary for compilation and linking is stored in project files and, hopefully there are special utilities, included in the C++Builder installation, which can automate this dirty work, provide necessary parameters to compilers and linker and run them. Their names are bpr2mak.exe and make.exe.
First you have to run bpr2mak.exe, passing your project *.bpr or *.bpk file as a parameter and then you will get a special *.mak file as output, which you can use to feed on make.exe, which finally will build your project.
Look at this simple cmd script:
#bpr2mak.exe YourProject.bpr
#ren YourProject.mak makefile
#make.exe
You can provide the real name of "YourProject.mak" as a parameter to make.exe, but the most straightforward way is to rename the *.mak file to "makefile", and then make.exe will find it.
To have different build options, you can do the following:
The first way: you can open your project in the IDE, edit options and save it with a different project name in the same folder (usually there are two project files for debug and release compile options). Then you can provide your building script with different *.bpr files. This way, it looks simple, because it doesn't involves scripting, but the user will have to manually maintain coherency of all project files if something changes (forms or units added and so on).
The second way is to make a script which edits the project file or make file. You will have to parse files, find compiler and linker related lines and put in the necessary keys. You can do it even in a cmd script, but surely a specialised scripting language like Python is preferable.
Use:
msbuild project.cbproj /p:config=[build configuration]
More specifics can be found in Building a Project Using an MSBuild Command.
A little detail not mentioned.
Suppose you have external dependencies and that the .dll file does not initially exist in your folder
You will need to include the external dependencies in the ILINK32.CFG file.
This file is usually in the folder
C:\Program Files (x86)\Borland\CBuilder6\Bin\ilink32.cfg
(consider your installation location)
In this file, place the note for your dependencies.
Example: A dependency for TeeChart, would look like this (consider the last parameter):
-L"C:\Program Files (x86)\Borland\CBuilder6\lib";"C:\Program Files (x86)\Borland\CBuilder6\lib\obj";"C:\Program Files (x86)\Borland\CBuilder6\lib\release";"C:\Program Files (x86)\Steema Software\TeeChart 805 for Builder 6\Builder6\Include\";"C:\Program Files (x86)\Steema Software\TeeChart 805 for Builder 6\Builder6\Lib\"
You will also need to include the -f command to compile.
In cmd, do:
//first generate the file.mak
1 - bpr2mak.exe MyProject.bpr
//then compile the .mak
2 - make.exe -f MyProject.mak
You can also generate a temporary mak file with another name, as the answer above says, directly with bpr2mak
bpr2mak.exe MyProject.bpr -oMyTempMak.mak