If I recompile a program when it is still running, will the program still be executed as the original before recompilation?
I just find some answers from Is it safe to recompile an executable while it's running?, but I have a more complicated situation:
I am working on a python package with C extension;
I may recompile just a shared object in that C extension;
I will have to submit it to the queue by "qsub"...
Thanks!
Related
As far as I know, the compiler compiles the code by converting it to a language that a computer can understand which is the machine language and this is done before running the code.
So, does the compiler compile my code each time I write a character in the file?
And if so, does it check the whole code? Or just the line that updated.
An important part to this question is the type of programming language(PL) we are talking about. Generally speaking, I would categorize PL into 3 groups:
Traditional PLs. Ex: C, C++, Rust
The compiler compiles the code into machine language when you hit the "build" button or the "run" button.
It doesn't compile every time you change the code, but a code linter does continuously observe your code and check it for errors.
Another note, when you change part of the code and compile it, the compiler doesn't recompile everything. It usually only recompile the current assembly file (or module or whatever you call them).
It is also important to note that a lot of modern IDEs, compile when you save the files.
There is also the hot reload feature. It is a smart compiler feature that can swap certain parts of the code while it is running.
Interpreted PLs Ex: python, JS and PHP
Those languages never get compiled; Rather, they get interpreted or translated into native code on the fly and in-memory when you run them.
Those languages usually employee a cache to accelerate the subsequent code execution.
Intermediary Code PL. Ex: Kotlin, java, C#
Have 2 stages of compilation:
Build time compilation.
Just in time (run-time) compilation.
Build time compilation converts the code into intermediary language (IL) machine code, which is special to the run-time.
This code only understood by the run time like Java runtime or dot net runtime
The second compilation happens when the programs get installed or ran for the first time. This is called just in time compilation (JIT)
The run-time convert the code into native code specific to the run-time OS.
How to directly run a c++ file present in read-only storage like CD-drive without making executable files using g++? There must be some arguments for that to work.
The process of a C/C++ program when you make one till you run it:
You write the program's source code.
The compiler comes in here and compiles the source code to object files.
Note: Remember that the program cannot be executed at this stage. It's only an object file. You'd know this if you have worked on bigger size programs, but if you haven't here is how it works. Remember using those header files in your programs? These header files just tell the compiler that there are some things that are not defined in your program. They are somewhere else. So your compile compiles the program to the object file leaving out things that have a prototype (which is in the header files).
This is a very important point. Here a program called 'linker' comes into play. What linker does is to take all the object files created by compiler and combines them into one. Say for example your compiler created a single object file. Now, you're using math library or anything from standard library. The compiler-linker package (often called only compiler) comes with object files for these standard library definitions. So, linker takes your object file and combines it with other object files from the package and then converts it to an executable file. This is the file that you can run. Nothing else is runnable directly.
To run source code the process is explained already, we have to use the g++. Now
What I understand from your question is that you want to know if a program can be run once it's compiled and linked properly (hence an executable has been generated). Answer to that would be yes.
Alternatively, may sound strange, there is an interpreter I know called Cling that can be of use to bypass the compilation of C++ program.
After all C++ is generally seen as a compiled language. However, any programming language can be implemented as a compiler or as an interpreter and Cling happens to be an interactive C++ interpreter based on LLVM and Clang.
Take a thorough look at this
I'm trying to understand how does golang's garbage collector work when the golang code is compiled and I guess when using go run as well. I figure go run is a little more straight forward and just runs the garbage collector along with the .go files you are running. But is the garbage collector compiled into the binaries as well when compiling to an executable?
The compiled object files do not contain any garbage collector "code".
When a program is run with go run, the go command will compile your sources, create and start an executable binary in a temp folder. See below.
When an application is compiled and linked into an executable binary, a go runtime is also included in the executable which is loaded when the binary is started. This runtime provides the garbage collector amongst other services such as runtime reflection and stacktrace information. This is the main reason why a simple Hello World application results in like a 2 MB executable binary.
I'm trying to port some very old fortran code to windows. I'd like to use mingw and f2c, which has no problem converting the code to usable C on OS X and Ubuntu. I used f2c.exe as distributed by netlib on a fresh install of mingw, and it translated the code fine. I have a "ported" version of libf2c that seems to still contain some unresolved references -- mostly file i/o routines (do_fio, f_open, s_wsfe, e_wsfe) and, peculiarly, one arithmetic routine (pow_dd). To resolve these issues, I tried to build libf2c from source, but ran into an issue during the make process. The make proceeds to dtime_.c, but then fails due to a dependency on sys/times.h, which is no longer a part of the mingw distro. There appears to be a struct defined in times.h that defines the size of a variable in dtime_.c, specifically t and t0 on lines 53 and 54 (error is "storage size of 't' isn't known"; same for t0).
The makefile was modified to use gcc, and make invoked with no other options passed.
Might anyone know of a workaround for this issue? I feel confident that once I have a properly compiled libf2c, I'll be able to link it with gcc and the code will work like it does on linux and os X.
FOLLOW-UP: I was able to build libf2c.a by commenting out the time related files in the makefile (my code does not contain any time related functions, so don't think it will matter). I copied it to a non-POSIX search directory as show in -print-search-dirs, specifically C:\MinGW\lib\gcc\mingw32\3.4.5. That seems to have fixed the issue on the unresolved references, although the need to eliminate the time files does concern me. While my code is now working, the original question stands -- how to handle makefiles that call for sys/times.h in mingw?
Are you sure the MinGW installation went correct? As far as I can tell the sys/times.h header is still there, in the package mingwrt-3.18-mingw32-dev.tar.gz. I'm not familiar with the gui installer, but perhaps you have to tick a box for the mingwrt dev component.
I'm porting an application to MacOS X - but the original developer's build system uses NMAKE, and ideally they'd like to keep it instead of switching to a new one.
I've managed to get NMAKE running under OSX using wine (built using MacPorts) and added Objective C support to the build files, and created a Unix-linked PE wrapper 'run.exe' which wine can load but uses POSIX to call back into things like gcc and ld, as is described on various places online as a means of escaping out of wine back into Unix.
However, I'm having a few specific issues. They're minor enough that I can get on with the port, but it does mean I need to run builds a few times sometimes, because of timing.
Basically, when wine.exe calls back into the shell and thus gcc, the link between child processes seems to be broken. gcc and ld will never return an error code even on failure, because they can't get the exit code from their spawned children. ar will actually print out it can't find its child and return immediately, causing problems when ld tries to link object files to libraries that are still being put together.
Has anyone else tried anything similar and seen the same problem, on OSX or elsewhere? Is there an obvious solution?
The Microsoft .NET Rotor (SSCLI) project includes source code, intended to be build on OSX and elsewhere. The Rotor source code includes the source code to NMake. So get Rotor working, then use it's Nmake. Even if you prefer to continue to use your Wine-based Nmake, you could probably learn from Rotor's use of Nmake on Unix, it's use of Gcc, etc.
If there is nothing that odd / inconsistent about the original developers build system, could you write an automatic conversion of their make files back into Unix make, and keep your builds 'native'?
(Builds being fraught enough anyway, without extra complications)