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ZhimingWang 09-05-2012 01:45 AM

How to compile (without building) a .c/.cpp file with Xcode?
 
First, I'll post my two questions at the very beginning in case you don't want to listen to me nagging about my personal circumstances:

1. How to compile without building a .c/.cpp file? Is it possible?
2. How to run my file without rebuilding? (Seems that Xcode builds the file before running whether or not the file has been built? Don't tell me to export the executable and run, though; I mean is there a command in Xcode...)

Environment: Xcode 4.4.1 on Mountain Lion.

OK, let me explain in details:
I'm switching from Dev C++ to Xcode. Yes, this is a silly question, but you know, beginners usually stuck with silly questions...X_X

Well, I'm running Xcode 4.4.1 on Mountain Lion. I have the habit to compile codes every several minutes to shorten the annoying debugging process in the end. However, I can't find the compile option. I can choose to build the file (I am working in a project, not a single file), but you know, building takes way more time than compiling, and it is not economical to build each time if the source code is considerably long. So here comes my first question:

1. How to compile without building a .c/.cpp file? Is it possible?

By the way, when I finished a .c/.cpp file, I Cmd+B to build it and succeeds. But when I Cmd+R to run, before the program started the "Building Succeeds" message appeared on the screen. Does it mean the file underwent the building process again? If it is so, it will waste a considerable amount of time, right? So here comes my second question:

2. How to run my file without rebuilding?

Thank you in advance of your kind help!:D

Raz0rEdge 09-07-2012 03:10 PM

What exactly does "compile without building" even mean? A quick primer on how this all works. A program can be comprised one one or multiple sources/header files..

If there is a single source file, it is first pre-processed by the compiler to evaluate all of the "#include", "#import", "#define", "#pragma" and other pre-processor directives. The file is then compiled into an object file, it is then finally linked against any necessary libraries to make it a functioning program.

The same process holds true for a project with multiple source files, you go through all the steps for each of the source files and deal with any cross-file dependencies as needed or report errors if things are messed up. Once it's all done, the final executable is created for execution.

Suppose you have a project with 3 source files, you modify one of them and then hit CMD+b, this will cause the compiler to determine which file changed, and go through the steps I described above and create the executable at that point. If you happen to do a CMD+r immediately after, the build will automatically run but since it's already up to date, nothing really happens except the message appearing and going to execute your program.

I'll have to check to see if there is a XCode option to prevent building when running, but that is usually a problem if you don't remember to build before you run.

Unless you are writing a VERY complicated program or running this on a Mac that is severely lacking in power, I can't imagine the few seconds it takes for the incremental builds or the minute it might take build the entire program is a huge deal.

I deal with building things that takes hours to complete so I know all about waiting..:)

ZhimingWang 09-07-2012 10:15 PM

Quote:

Originally Posted by Raz0rEdge (Post 1445594)
What exactly does "compile without building" even mean? A quick primer on how this all works. A program can be comprised one one or multiple sources/header files..

If there is a single source file, it is first pre-processed by the compiler to evaluate all of the "#include", "#import", "#define", "#pragma" and other pre-processor directives. The file is then compiled into an object file, it is then finally linked against any necessary libraries to make it a functioning program.

The same process holds true for a project with multiple source files, you go through all the steps for each of the source files and deal with any cross-file dependencies as needed or report errors if things are messed up. Once it's all done, the final executable is created for execution.

Suppose you have a project with 3 source files, you modify one of them and then hit CMD+b, this will cause the compiler to determine which file changed, and go through the steps I described above and create the executable at that point. If you happen to do a CMD+r immediately after, the build will automatically run but since it's already up to date, nothing really happens except the message appearing and going to execute your program.

I'll have to check to see if there is a XCode option to prevent building when running, but that is usually a problem if you don't remember to build before you run.

Unless you are writing a VERY complicated program or running this on a Mac that is severely lacking in power, I can't imagine the few seconds it takes for the incremental builds or the minute it might take build the entire program is a huge deal.

I deal with building things that takes hours to complete so I know all about waiting..:)

Hi Ashwin,

Thank you for your really long reply:)

As for "compile without building", I mean the process that you compile the source file, generate the .obj file but don't link them, so no executables are generated. I mainly use this for grammatical check. (Seems that Xcode does this as I'm typing? Will that kind of check work in complex situations - I mean, will Xcode point out all errors in syntax?) I previously worked on Dev C++ on PC, and there was the option to compile, OR build. If my memory doesn't fail me, it usually takes five to six times longer to build a project than to compile it...

Anyway, I'm merely a college undergraduate and an amateur coder, so it typically take no longer than half a minute to build my projects.;) The waiting time becomes annoying only in the debugging process. Well, neither compiling without building nor running without rebuilding helps in debugging, though, unless I miss the bug and have to step into the same executable again...:\

Raz0rEdge 09-08-2012 08:05 AM

Xcode does indeed parse your code as you are typing and will point out blatant syntax errors or missing imports, declarations or unused variables and so on. It you fix most of these things before you compile, then the errors that are encountered are compile/linking errors that couldnt have been detected by a syntax check anyway..

ZhimingWang 09-08-2012 10:19 AM

Quote:

Originally Posted by Raz0rEdge (Post 1445722)
Xcode does indeed parse your code as you are typing and will point out blatant syntax errors or missing imports, declarations or unused variables and so on. It you fix most of these things before you compile, then the errors that are encountered are compile/linking errors that couldnt have been detected by a syntax check anyway..

Got it. Thank you Ashwin!

smallmountain 08-12-2013 09:22 AM

Could this be correct? XCode will not let you simply compile a .cpp file to its object file without building the entire project? Visual Studio lets you do this. It is very helpful when you are changing a header file, say with templates in it, that is widely included in your project, but only one or two source files use the template class or function that you are trying to get right. I like to compile the .cpp file to make sure I don't have a stupid error, and then once the .cpp file compiles, then I fire up a build that might take 10 minutes. Maybe I have link errors after the build, so I repeat the cycle, but at least I am not waiting 10 minutes to find out I have a simple error.

smallmountain 08-13-2013 10:59 AM

My understanding is that with XCode 5, you will be able to compile a single C++ file just like you can in Visual Studio.

cptkrf 08-27-2013 10:46 AM

You can drop to a terminal and just compile the c/cpp source with GCC just as if you were on a plain Unix or Linux machine.

In fact, if you are making c/cpp programs you don't need Xcode at all, just download the Command Line Utilities and use textedit for the source. (Note. if you are making gui obj-c stuff, you have to have Xcode.)

The simplest compile will be with the gcc command and the source file name. i.e. gcc helloworld.c

man gcc will give you the manual for the options.


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