Free Pascal on OSv: what changed

Revision 0 to 1. Removed lines have a minus sign; added lines have a plus sign.

Title: Free Pascal on OSv

New		Line
1	+	# OSv
2	+
3	+	OSv is an operating system based on Linux optimized for the cloud. [Official page](http://osv.io/) It runs a single application together with a small kernel and all needed libraries in a virtual machine. That means to run OSv applications you need to install a hypervisor such as QEMU/KVM or VirtualBox.
4	+
5	+	# Installation
6	+
7	+	## Install OSv on Linux
8	+
9	+	This worked on 3rd Mar 2015 on Ubuntu 14.10 and on 3rd Sep 2016 on Ubuntu 16.04:
10	+
11	+	Please read <http://osv.io/run-locally/>. Especially about the "Data collection".
12	+
13	+	Downloading capstan to ~/bin/capstan:
14	+
15	+	`curl `[`https://raw.githubusercontent.com/cloudius-systems/capstan/master/scripts/download`](https://raw.githubusercontent.com/cloudius-systems/capstan/master/scripts/download)` \| bash`
16	+
17	+	Install needed qemu-kvm (VirtualBox is also possible, but not handled in this document)
18	+
19	+	`sudo apt-get install qemu-kvm`
20	+
21	+	# Building an instance with capstan
22	+
23	+	Capstan takes a basic image and adds your libraries to create a VM image. It then starts the VM and runs the 'main' function of your library. At the moment only Linux/amd64 dynamic libraries with PIC are supported.
24	+
25	+	## Capstanfile
26	+
27	+	Capstan needs a config file named Capstanfile. Read [here](https://github.com/cloudius-systems/capstan/blob/master/Documentation/Capstanfile.md) for details.
28	+
29	+	Create a directory for the example. For instance ~/osv_fpc_test.
30	+
31	+	Here is an example config for a hello world program (~/osv_fpc_test/Capstanfile):
32	+
33	+	# Name of the base image. Capstan will download this automatically from Capstan repository.
34	+	base: cloudius/osv-base
35	+
36	+	# The command line passed to OSv to start up the application.
37	+	cmdline: /tools/hello.so
38	+
39	+	# The command used to build the application.
40	+	build: ./compile.sh
41	+
42	+	# List of files that are included in the generated image.
43	+	files:
44	+	/tools/hello.so: hello.so
45	+
46	+	## Pascal Library
47	+
48	+	The small Linux kernel does not support all syscalls needed by the default FPC Linux System unit.
49	+
50	+	See here for some details what OSv does not support: <https://github.com/cloudius-systems/osv/wiki/Porting-native-applications-to-OSv>
51	+
52	+	You need to build the System unit using Libc (tested with fpc trunk revision 34418):
53	+
54	+	`cd fpc_src_3.1.1`\
55	+	`make clean all OPT='-dFPC_USE_LIBC -Fl/usr/lib/gcc/x86_64-linux-gnu/5'`\
56	+	`sudo make install INSTALL_PREFIX=/usr`
57	+
58	+	## hello.pas
59	+
60	+	``` pascal
61	+	library hello;
62	+
63	+	// start function for OSv
64	+	function main: longint; cdecl;
65	+	begin
66	+	Writeln('It works!');
67	+	main:=0;
68	+	end;
69	+
70	+	exports main name 'main'; // OSv searches for 'main' in the library
71	+
72	+	end.
73	+	```
74	+
75	+	Here is the ~/osv_fpc_test/compile.sh:
76	+
77	+	#!/bin/bash
78	+	# create a dynamically linked library hello.so
79	+	/usr/lib/fpc/3.1.1/ppcx64 -fPIC -XD -Xc -gw2 -ohello.so hello.pas
80	+
81	+	## Building
82	+
83	+	Note: The first time you build, capstan will download the base VM image "cloudius/osv-base" (~/.capstan/).
84	+
85	+	[]$ cd ~/osv_fpc_test
86	+	[]$ ~/bin/capstan build
87	+	Building osv...
88	+	Uploading files...
89	+	1 / 1 [===================================] 100.00 %
90	+
91	+	## Running
92	+
93	+	[]$ ~/bin/capstan run
94	+	Created instance: helloworld
95	+	OSv v0.18
96	+	eth0: 192.168.122.15
97	+	It works!
98	+
99	+	# Pascal Library without using the System unit
100	+
101	+	As demonstration here is a library, that does not call the system unit (works the normal FPC system unit):
102	+
103	+	## hello.pas
104	+
105	+	Here is the ~/osv_fpc_test/hello.pas:
106	+
107	+	``` pascal
108	+	library hello;
109	+
110	+	uses
111	+	unixtype;
112	+
113	+	// use the C function 'write'
114	+	function CWrite(fd : cInt; buf:pChar; nbytes : unixtype.TSize): TSsize; external name 'write';
115	+
116	+	// start function for OSv
117	+	function main: longint; cdecl;
118	+	const
119	+	MyText: PChar = 'It works!'#10;
120	+	begin
121	+	CWrite(StdOutputHandle,MyText,strlen(MyText));
122	+	main:=0;
123	+	end;
124	+
125	+	exports main name 'main'; // OSv searches for 'main' in the library
126	+
127	+	end.
128	+	```
129	+
130	+	## Compile a library that does not call the system init
131	+
132	+	Here is the ~/osv_fpc_test/compile.sh:
133	+
134	+	#!/bin/bash
135	+
136	+	# compile without linking, create a dynamically linked library hello.so
137	+	fpc -fPIC -XD -Xc -g -s -ohello.so hello.pas
138	+	# link without -init FPC_SHARED_LIB_START -fini FPC_LIB_EXIT
139	+	/usr/bin/ld -b elf64-x86-64 -m elf_x86_64 -soname hello.so -shared -L. -o hello.so link.res
140	+
141	+	## Building
142	+
143	+	Note: The first time you build, capstan will download the base VM image "cloudius/osv-base" (~/.capstan/).
144	+
145	+	[]$ cd ~/osv_fpc_test
146	+	[]$ ~/bin/capstan build
147	+	Building osv...
148	+	Uploading files...
149	+	1 / 1 [===================================] 100.00 %
150	+
151	+	## Running
152	+
153	+	[]$ cd ~/osv_fpc_test
154	+	[]$ ~/bin/capstan run
155	+	Created instance: osv
156	+	OSv v0.18
157	+	eth0: 192.168.122.15
158	+	It works!
159	+
160	+	---
161	+	From the Free Pascal wiki, page "Free Pascal on OSv", as it stood on 2020-02-16 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
162	+	Category: Linux

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