I'm new to OCaml, but I'm trying to figure out the equivalent of __filename, __dirname from Node. That is, I need to build a path relative to the file containing the code in question.
For reference, I'm working through Ghuloum's IACC: http://ell.io/tt$ocameel
I'm building my first compiler, and I have an utterly-simplistic ‘runtime’ file (in C — temporarily) adjacent to the compiler's source-code. I need to be able to pass the path to this file, as an argument (or a pre-compiled version, I suppose) to gcc or my linker, to have it linked against my compiler's output when I invoke the linker/assembler tooling.
(This may be a stupid question — I'm at a bit of an unknown-unknown here, “how does a compiler get the runtime to the linker”, or something like that. Any commentary about idiomatic solutions to this is welcome, even if it's not a direct answer to the above question!)
If you're running the source file directly via ocaml myfile.ml, Sys.argv.(0) will give you the path to the source file and you can use Filename.dirname to get the directory from that.
If you first compile the source file into an executable and then run the executable, Sys.argv.(0) will give you the name of the executable. In that scenario it's impossible to get the location of the source code (especially if you consider that the person running the executable might not even have the source code on their system).
If you set up your project structure, so that your sources live in src/, your compiled binary in bin/ and the compiled stdlib in lib/, you could just use Filename.dirname Sys.argv.(0) ^ "../lib" as the library path for gcc. This will work whether you run ocaml src/mycompiler.ml, bin/mycompiler or just mycompiler after installing everything to /usr/ or /usr/local/.
Related
To learn the processes behind compilation of Ada programs (without resorting to using gpr), I've decided to compile one of my projects manually. To compile a program, I run the following command on each .adb file therein (not manually, however):
$ gcc -c src/<file>.adb -o obj/<file>.o
That compiles all the files and puts them in the obj directory.
Or rather, it would. There is a slight problem with this. I have an archive (static library) that I've generated from another project, called libapples.a, containing package Apples. The Apples package is used by the files you see me compiling above.
Since libapples.a doesn't have source files anymore (given its archive format), it's not viable (not even possible) to provide the sources of that library to the command above using -I switches; on the other hand, if I don't have the sources included, the command above comes back to me saying:
<file>.adb:<y>:<x>: file "apples.ads" not found
gnatmake: "src/<file>.adb" compilation error
I've attempted to include the library in the compilation process by using flags -L and l (which I believe is how you'd do it in C; feel free to correct me if I'm wrong). In another attempt I placed the archive right in the source directory.
How does one go about including a library in the compilation process?
apples.ads is somewhat like a header in C and you definitely need it for your file to compile. You should use -I to point gcc to the directory where apples.ads is located in.
Be aware that compiling an Ada source not only yields an object file, but also an Ada Library Information (.ali) file. You'll need that for the next step. You should not use the -o flag because it may lead to your .o and .ali files having different names.
On the other hand, since you only want to produce an object file, you should use -c to tell gcc to only compile. In other languages like C, gcc compiles and links by default; in Ada, the process is more complex.
After compilation, you need to call gnatbind on the .ali file of your main program. This generates a package that will take care of proper initialization of everything. To do that, gnatbind needs the .ali file of the Apples package! You can specify the .ali search directory with -aO.
Finally, gnatlink called on the main .ali file will link everything together. It figures out itself which object files and libraries it needs. It will append the necessary options to the linker, including the reference to libapples.a. It also compiles the package generated by gnatlink.
I don't know exactly what gnatlink will do under the hood; you could probably compile the package generated by gnatbind manually and then call the linker if you can figure out the proper arguments.
I have downloaded a large software project FriCAS which I have compiled from source and using SBCL. This was just a matter of using GNU .configure - I am a complete Lisp newbie.
However, in order to add some further functionality I have - by very carefully following directions - installed quicklisp and a few extra packages. So far so good.
Here's my issue: I am trying to compile an external lisp file for use in the system. I need to make quicklisp and its packages visible to the compiler. So I've copied my .sbclrc file to the top of my lisp file:
#-quicklisp
(let ((quicklisp-init (merge-pathnames "quicklisp/setup.lisp"
(user-homedir-pathname))))
(when (probe-file quicklisp-init)
(load quicklisp-init)))
I have followed this with
(eval-when (:compile-toplevel)
(ql:quickload "f2cl-lib"))
I have already installed f2cl-lib with quicklisp. However, my compiler (within FriCAS) immediately aborts with
; caught ERROR:
; READ error during COMPILE-FILE:
;
; Package QL does not exist.
I'm a bit stumped here - there's probably something trivial and obvious which is missing, but as I say from a newbie perspective I don't know what it is.
Looks like a FAQ. See also the documentation for eval-when.
The File Compiler
Remember, a file compiler compiles forms and does not execute them. It just generates code for later execution. Generally. Though, in Common Lisp there are some exceptions to this rule: for example a macro, used in the source code, will be run by the file compiler. But Common Lisp also allows us to tell the file compiler to execute code at compile time, that's one of the use cases of eval-when.
Your example simplified
If you have a file:
(load "file-which-creates-package-foo")
(eval-when (:compile-toplevel)
(foo:bar))
Then the file compiler will generate code for loading the file, but it will not load the file.
Next, the file compiler sees a second form, where the file compiler is instructed to execute a statement at compile time (and only at compile time), so (foo:bar) will be executed at compile time. But it is worse: Since the loading code has not been executed yet, the package FOO is unknown, and the form (foo:bar) will be read at compile time, the reader already complains at compile time that the package FOO does not exist.
The use of EVAL-WHEN
What you need to do, is to tell the file compiler to actually load the stuff it needs during compilation. The file already contains an eval-when form, so that should give you a hint: use eval-when. It has three situations:
:compile-toplevel -> the file compiler executes the enclosed forms
:load-toplevel -> the file compiler generates code so that the code will be executed when loading the code
:execute
Make sure that those situations are mentioned, when the code should be executed.
Possible solutions
So there are possible solutions:
as above, use EVAL-WHEN to be able to execute forms by the file compiler
write the loading code into a separate file and compile/load this file before you use the package. One could also add this file to a system such that it will be loaded by the compiling the system, before the using code will be compiled.
I have a solution with various projects, one of which is the main executable, and the rest are libraries the executable depends on. Each one compiles and links fine. However, trying to start the executable gives weird results. Using ldd, I see that the executable is trying to find libraries like so:
../bin/debug/libBlahBlah.so => not found
However, for each project, I'm declaring "bin/debug" (which is the output directory for these libraries) as a libdirs entry, and linking against the library by adding "BlahBlah" as a link, where "BlahBlah" is the name of the project.
I'm not even sure how to accomplish this without premake. Any help is appreciated.
The original intention was to have the library sit next to the executable then set an RPATH that searched for the library next to executable. With the way it is now, it searches for that absolute path relative to the executable... I cannot figure out how to get it off.
I'm using premake5. I've tried to use the nightly and compiling myself. Upstream is currently not compiling however.
If you are using the latest alpha or source of Premake5, you can use the "RelativeLinks" flag to use -L/-l instead of relative paths to libraries:
project "MyProject"
flags "RelativeLinks"
You will still need to set up the rpath properly though; you can do that with buildoptions() and the appropriate command line flags for your compiler. Maybe (untested):
buildoptions "-Wl,-rpath=."
That should work in Premake 4 as well.
I created simple Java Servlet: WelcomeServlet.java.
Than, I tried compile this file via:
javac WelcomeServlet.java
In result I see compile error:
package javax.servlet doesn't exit
I try find solution for this error with Google. And I find first part of answer: java compiler doesnt see servlet-api.jar file.
I know, that Apache Tomcat in it lib folder contains servlet-api.jar file.
So, I have this file, but where I must copy this file??
I try different folders:
echo %JAVA_HOME%
C:\Program Files\Java\jdk1.6.0_26
%PATH% contains this line: C:\Program Files\Java\jdk1.6.0_26\bin
So, I copy in:
%JAVA_HOME%\bin
%JAVA_HOME%\lib
%JAVA_HOME%\jre\lib
And in result same error.
And only after I copy servlet-api.jar in directory:
%JAVA_HOME%\jre\lib\ext
compilation complite sucessful.
My question: Why? Why I must copy in folder %JAVA_HOME%\jre\lib\ext ??
Where This moment describe in documentation?
And other question we have some official docs or specifications that describe folder structure for jdk folder??
You'll need to specify the directory or directories you want the compiler to search by using the -classpath command line option when running javac. The reason the compiler found your .jar in %JAVA_HOME%\jre\lib\ext is because it searches the extension directories by default.
This is for Java 1.5, but I believe it is more or less still correct:
http://docs.oracle.com/javase/1.5.0/docs/tooldocs/findingclasses.html
The link Shaun provides is a more complete answer. But in short, using the classpath is the best way to introduce 3rd party or external (to the JDK/JRE) libraries. The classpath is a concept much like the %PATH% or the $PATH variables, but specifies locations for java to use for lookup rather than the shell to use for lookup of executables.
The classpath provides the java compiler or java virtual machine a list of items to use when searching for resources. This "path" may include directories or files. It will typically include jar files and sometimes locations of configuration files. Many Java based lookup schemes for files configuration or otherwise use some variant of what is accomplished by [Class#getResourceAsStream()][1]'s use of walking the Classpath.
I have rarely seen an incident where putting a jar file in the lib/ext location was preferred to utilizing the Classpath.
The classpath is typically an environment variable (%CLASSPATH% or $CLASSPATH) or specified on the command line when running java or javac (e.g. -cp or -classpath see the help from the executable you are running).
Build tools such as Ant and Maven will also provide abstractions to defining the list of jars to be utilized by your applications and are highly recommended to be used for any length of repetitive change code, build, test, run cycles.
I am a bit confused by the way qt handles libraries. My plan was to put the external libraries I need into the source directory, so that a do not have to install them into the system. As this doesn't seem to work (see below) I was wondering, if this is generally a bad idea or if there is some trick to it??
So I compiled the libraries and put them into /mysubdir. In the .pro-file I added
LIBS+= -L"mysubdir" -l"mylib"
I got the compiler error [projectname] Error 2 and don't know what it means.
The argument passed to -L must be an absolute path. Please give it a try with a full path, or at least -L./wcslibc. Though I'm not sure whether ./ will be recognized correctly. You can get the current path in qmake like this:
LIBS += -L$${PWD}/wcslibc -lwcs