Author:	Andreas Rumpf
Version:	0.9.3

"Look at you, hacker. A pathetic creature of meat and bone, panting and sweating as you run through my corridors. How can you challenge a perfect, immortal machine?"

Introduction

This document describes the usage of the Nimrod compiler on the different supported platforms. It is not a definition of the Nimrod programming language (therefore is the manual).

Nimrod is free software; it is licensed under the MIT License.

Compiler Usage

Command line switches

Basic command line switches are:

Usage:

nimrod command [options] [projectfile] [arguments]

Command:

compile, c	compile project with default code generator (C)
doc	generate the documentation for inputfile
doc2	generate the documentation for the whole project
i	start Nimrod in interactive mode (limited)

Arguments:

arguments are passed to the program being run (if --run option is selected)

Options:

-p, --path:PATH	add path to search paths
-d, --define:SYMBOL	define a conditional symbol
-u, --undef:SYMBOL	undefine a conditional symbol
-f, --forceBuild	force rebuilding of all modules
--stackTrace:on|off	turn stack tracing on|off
--lineTrace:on|off	turn line tracing on|off
--threads:on|off	turn support for multi-threading on|off
-x, --checks:on|off	turn all runtime checks on|off
--objChecks:on|off	turn obj conversion checks on|off
--fieldChecks:on|off	turn case variant field checks on|off
--rangeChecks:on|off	turn range checks on|off
--boundChecks:on|off	turn bound checks on|off
--overflowChecks:on|off	turn int over-/underflow checks on|off
-a, --assertions:on|off	turn assertions on|off
--floatChecks:on|off	turn all floating point (NaN/Inf) checks on|off
--nanChecks:on|off	turn NaN checks on|off
--infChecks:on|off	turn Inf checks on|off
--deadCodeElim:on|off	whole program dead code elimination on|off
--opt:none|speed|size	optimize not at all or for speed|size
--app:console|gui|lib|staticlib	generate a console app|GUI app|DLL|static library
-r, --run	run the compiled program with given arguments
--advanced	show advanced command line switches
-h, --help	show this help

Advanced command line switches are:

Advanced commands:

compileToC, cc	compile project with C code generator
compileToCpp, cpp	compile project to C++ code
compileToOC, objc	compile project to Objective C code
rst2html	convert a reStructuredText file to HTML
rst2tex	convert a reStructuredText file to TeX
buildIndex	build an index for the whole documentation
run	run the project (with Tiny C backend; buggy!)
genDepend	generate a DOT file containing the module dependency graph
dump	dump all defined conditionals and search paths
check	checks the project for syntax and semantic
idetools	compiler support for IDEs: possible options: --track:FILE,LINE,COL track a file/cursor position --trackDirty:DIRTY_FILE,ORIG_FILE,LINE,COL track a file, currently not saved to disk --suggest suggest all possible symbols at position --def list all possible definitions at position --context list possible invokation context --usages list all usages of the symbol at position --eval evaluates an expression serve start the compiler as a service mode (CAAS) --server.type:TYPE either stdin or tcp --server.port:PORT port for tcp mode, by default 6000 --server.address:HOST binds to that address, by default ""

Advanced options:

-m, --mainmodule:FILE	set the project main module
-o, --out:FILE	set the output filename
--stdout	output to stdout
--listFullPaths	list full paths in messages
-w, --warnings:on|off	turn all warnings on|off
--warning[X]:on|off	turn specific warning X on|off
--hints:on|off	turn all hints on|off
--hint[X]:on|off	turn specific hint X on|off
--lib:PATH	set the system library path
--import:PATH	add an automatically imported module
--include:PATH	add an automatically included module
--nimcache:PATH	set the path used for generated files
--header:FILE	the compiler should produce a .h file (FILE is optional)
-c, --compileOnly	compile only; do not assemble or link
--noLinking	compile but do not link
--noMain	do not generate a main procedure
--genScript	generate a compile script (in the 'nimcache' subdirectory named 'compile_$project$scriptext')
--os:SYMBOL	set the target operating system (cross-compilation)
--cpu:SYMBOL	set the target processor (cross-compilation)
--debuginfo	enables debug information
--debugger:on|off	turn Embedded Nimrod Debugger on|off
-t, --passC:OPTION	pass an option to the C compiler
-l, --passL:OPTION	pass an option to the linker
--cincludes:DIR	modify the C compiler header search path
--clibdir:DIR	modify the linker library search path
--clib:LIBNAME	link an additional C library (you should omit platform-specific extensions)
--genMapping	generate a mapping file containing (Nimrod, mangled) identifier pairs
--project	document the whole project (doc2)
--lineDir:on|off	generation of #line directive on|off
--embedsrc	embeds the original source code as comments in the generated output
--threadanalysis:on|off	turn thread analysis on|off
--tlsEmulation:on|off	turn thread local storage emulation on|off
--taintMode:on|off	turn taint mode on|off
--symbolFiles:on|off	turn symbol files on|off (experimental)
--implicitStatic:on|off	turn implicit compile time evaluation on|off
--patterns:on|off	turn pattern matching on|off
--skipCfg	do not read the general configuration file
--skipUserCfg	do not read the user's configuration file
--skipParentCfg	do not read the parent dirs' configuration files
--skipProjCfg	do not read the project's configuration file
--gc:refc|v2|markAndSweep|boehm|none	select the GC to use; default is 'refc'
--index:on|off	turn index file generation on|off
--putenv:key=value	set an environment variable
--babelPath:PATH	add a path for Babel support
--excludePath:PATH	exclude a path from the list of search paths
--dynlibOverride:SYMBOL	marks SYMBOL so that dynlib:SYMBOL has no effect and can be statically linked instead; symbol matching is fuzzy so that --dynlibOverride:lua matches dynlib: "liblua.so.3"
--listCmd	list the commands used to execute external programs
--parallelBuild=0|1|...	perform a parallel build value = number of processors (0 for auto-detect)
--verbosity:0|1|2|3	set Nimrod's verbosity level (1 is default)
--cs:none|partial	set case sensitivity level (default: none); do not use! this setting affects the whole language
-v, --version	show detailed version information

List of warnings

Each warning can be activated individually with --warning[NAME]:on|off or in a push pragma.

Name	Description
CannotOpenFile	Some file not essential for the compiler's working could not be opened.
OctalEscape	The code contains an unsupported octal sequence.
Deprecated	The code uses a deprecated symbol.
ConfigDeprecated	The project makes use of a deprecated config file.
SmallLshouldNotBeUsed	The letter 'l' should not be used as an identifier.
AnalysisLoophole	The thread analysis was incomplete due to an indirect call.
DifferentHeaps	The code mixes different local heaps in a very dangerous way.
WriteToForeignHeap	The code contains a threading error.
EachIdentIsTuple	The code contains a confusing var declaration.
ShadowIdent	A local variable shadows another local variable of an outer scope.
User	Some user defined warning.

Verbosity levels

Level	Description
0	Minimal output level for the compiler.
1	Displays compilation of all the compiled files, including those imported by other modules or through the compile pragma. This is the default level.
2	Displays compilation statistics, enumerates the dynamic libraries that will be loaded by the final binary and dumps to standard output the result of applying a filter to the source code if any filter was used during compilation.
3	In addition to the previous levels dumps a debug stack trace for compiler developers.

Configuration files

Note: The project file name is the name of the .nim file that is passed as a command line argument to the compiler.

The nimrod executable processes configuration files in the following directories (in this order; later files overwrite previous settings):

1. $nimrod/config/nimrod.cfg, /etc/nimrod.cfg (UNIX) or %NIMROD%/config/nimrod.cfg (Windows). This file can be skipped with the --skipCfg command line option.
2. /home/$user/.config/nimrod.cfg (UNIX) or %APPDATA%/nimrod.cfg (Windows). This file can be skipped with the --skipUserCfg command line option.
3. $parentDir/nimrod.cfg where $parentDir stands for any parent directory of the project file's path. These files can be skipped with the --skipParentCfg command line option.
4. $projectDir/nimrod.cfg where $projectDir stands for the project file's path. This file can be skipped with the --skipProjCfg command line option.
5. A project can also have a project specific configuration file named $project.nimrod.cfg that resides in the same directory as $project.nim. This file can be skipped with the --skipProjCfg command line option.

Command line settings have priority over configuration file settings.

The default build of a project is a debug build. To compile a release build define the release symbol:

nimrod c -d:release myproject.nim

Search path handling

Nimrod has the concept of a global search path (PATH) that is queried to determine where to find imported modules or include files. If multiple files are found an ambiguity error is produced.

nimrod dump shows the contents of the PATH.

However before the PATH is used the current directory is checked for the file's existance. So if PATH contains $lib and $lib/bar and the directory structure looks like this:

$lib/x.nim
$lib/bar/x.nim
foo/x.nim
foo/main.nim
other.nim

And main imports x, foo/x is imported. If other imports x then both $lib/x.nim and $lib/bar/x.nim match and so the compiler should reject it. Currently however this check is not implemented and instead the first matching file is used.

Generated C code directory

The generated files that Nimrod produces all go into a subdirectory called nimcache in your project directory. This makes it easy to delete all generated files.

However, the generated C code is not platform independent. C code generated for Linux does not compile on Windows, for instance. The comment on top of the C file lists the OS, CPU and CC the file has been compiled for.

Compilation cache

Warning: The compilation cache is still highly experimental!

The nimcache directory may also contain so called rod or symbol files. These files are pre-compiled modules that are used by the compiler to perform incremental compilation. This means that only modules that have changed since the last compilation (or the modules depending on them etc.) are re-compiled. However, per default no symbol files are generated; use the --symbolFiles:on command line switch to activate them.

Unfortunately due to technical reasons the --symbolFiles:on needs to aggregate some generated C code. This means that the resulting executable might contain some cruft even when dead code elimination is turned on. So the final release build should be done with --symbolFiles:off.

Due to the aggregation of C code it is also recommended that each project resists in its own directory so that the generated nimcache directory is not shared between different projects.

Cross compilation

To cross compile, use for example:

nimrod c --cpu:i386 --os:linux --compile_only --gen_script myproject.nim

Then move the C code and the compile script compile_myproject.sh to your Linux i386 machine and run the script.

Another way is to make Nimrod invoke a cross compiler toolchain:

nimrod c --cpu:arm --os:linux myproject.nim

For cross compilation, the compiler invokes a C compiler named like $cpu.$os.$cc (for example arm.linux.gcc) and the configuration system is used to provide meaningful defaults. For example for ARM your configuration file should contain something like:

arm.linux.gcc.path = "/usr/bin"
arm.linux.gcc.exe = "arm-linux-gcc"
arm.linux.gcc.linkerexe = "arm-linux-gcc"

DLL generation

Nimrod supports the generation of DLLs. However, there must be only one instance of the GC per process/address space. This instance is contained in nimrtl.dll. This means that every generated Nimrod DLL depends on nimrtl.dll. To generate the "nimrtl.dll" file, use the command:

nimrod c -d:release lib/nimrtl.nim

To link against nimrtl.dll use the command:

nimrod c -d:useNimRtl myprog.nim

Note: Currently the creation of nimrtl.dll with thread support has never been tested and is unlikely to work!

Additional compilation switches

The standard library supports a growing number of useX conditional defines affecting how some features are implemented. This section tries to give a complete list.

Define	Effect
release	Turns off runtime checks and turns on the optimizer.
useWinAnsi	Modules like os and osproc use the Ansi versions of the Windows API. The default build uses the Unicode version.
useFork	Makes osproc use fork instead of posix_spawn.
useNimRtl	Compile and link against nimrtl.dll.
useMalloc	Makes Nimrod use C's malloc instead of Nimrod's own memory manager. This only works with gc:none.
useRealtimeGC	Enables support of Nimrod's GC for soft realtime systems. See the documentation of the gc for further information.
nodejs	The JS target is actually node.js.
ssl	Enables OpenSSL support for the sockets module.
memProfiler	Enables memory profiling for the native GC.

Additional Features

This section describes Nimrod's additional features that are not listed in the Nimrod manual. Some of the features here only make sense for the C code generator and are subject to change.

NoDecl pragma

The noDecl pragma can be applied to almost any symbol (variable, proc, type, etc.) and is sometimes useful for interoperability with C: It tells Nimrod that it should not generate a declaration for the symbol in the C code. For example:

var
  EACCES {.importc, noDecl.}: cint # pretend EACCES was a variable, as
                                   # Nimrod does not know its value

However, the header pragma is often the better alternative.

Note: This will not work for the LLVM backend.

Header pragma

The header pragma is very similar to the noDecl pragma: It can be applied to almost any symbol and specifies that it should not be declared and instead the generated code should contain an #include:

type
  PFile {.importc: "FILE*", header: "<stdio.h>".} = distinct pointer
    # import C's FILE* type; Nimrod will treat it as a new pointer type

The header pragma always expects a string constant. The string contant contains the header file: As usual for C, a system header file is enclosed in angle brackets: <>. If no angle brackets are given, Nimrod encloses the header file in "" in the generated C code.

Note: This will not work for the LLVM backend.

IncompleteStruct pragma

The incompleteStruct pragma tells the compiler to not use the underlying C struct in a sizeof expression:

type
  TDIR* {.importc: "DIR", header: "<dirent.h>",
          final, pure, incompleteStruct.} = object

Compile pragma

The compile pragma can be used to compile and link a C/C++ source file with the project:

{.compile: "myfile.cpp".}

Note: Nimrod computes a CRC checksum and only recompiles the file if it has changed. You can use the -f command line option to force recompilation of the file.

Link pragma

The link pragma can be used to link an additional file with the project:

{.link: "myfile.o".}

PassC pragma

The passC pragma can be used to pass additional parameters to the C compiler like you would using the commandline switch --passC:

{.passC: "-Wall -Werror".}

Note that you can use gorge from the system module to embed parameters from an external command at compile time:

{.passC: gorge("pkg-config --cflags sdl").}

PassL pragma

The passL pragma can be used to pass additional parameters to the linker like you would using the commandline switch --passL:

{.passL: "-lSDLmain -lSDL".}

Note that you can use gorge from the system module to embed parameters from an external command at compile time:

{.passL: gorge("pkg-config --libs sdl").}

Emit pragma

The emit pragma can be used to directly affect the output of the compiler's code generator. So it makes your code unportable to other code generators/backends. Its usage is highly discouraged! However, it can be extremely useful for interfacing with C++ or Objective C code.

Example:

{.emit: """
static int cvariable = 420;
""".}

proc embedsC() {.noStackFrame.} =
  var nimrodVar = 89
  # use backticks to access Nimrod symbols within an emit section:
  {.emit: """fprintf(stdout, "%d\n", cvariable + (int)`nimrodVar`);""".}

embedsC()

ImportCpp pragma

The importcpp pragma can be used to import C++ methods. The generated code then uses the C++ method calling syntax: obj->method(arg). In addition with the header and emit pragmas this allows sloppy interfacing with libraries written in C++:

# Horrible example of how to interface with a C++ engine ... ;-)

{.link: "/usr/lib/libIrrlicht.so".}

{.emit: """
using namespace irr;
using namespace core;
using namespace scene;
using namespace video;
using namespace io;
using namespace gui;
""".}

const
  irr = "<irrlicht/irrlicht.h>"

type
  TIrrlichtDevice {.final, header: irr, importc: "IrrlichtDevice".} = object
  PIrrlichtDevice = ptr TIrrlichtDevice

proc createDevice(): PIrrlichtDevice {.
  header: irr, importc: "createDevice".}
proc run(device: PIrrlichtDevice): bool {.
  header: irr, importcpp: "run".}

The compiler needs to be told to generate C++ (command cpp) for this to work. The conditional symbol cpp is defined when the compiler emits C++ code.

ImportObjC pragma

The importobjc pragma can be used to import Objective C methods. The generated code then uses the Objective C method calling syntax: [obj method param1: arg]. In addition with the header and emit pragmas this allows sloppy interfacing with libraries written in Objective C:

# horrible example of how to interface with GNUStep ...

{.passL: "-lobjc".}
{.emit: """
#include <objc/Object.h>
@interface Greeter:Object
{
}

- (void)greet:(long)x y:(long)dummy;
@end

#include <stdio.h>
@implementation Greeter

- (void)greet:(long)x y:(long)dummy
{
        printf("Hello, World!\n");
}
@end

#include <stdlib.h>
""".}

type
  TId {.importc: "id", header: "<objc/Object.h>", final.} = distinct int

proc newGreeter: TId {.importobjc: "Greeter new", nodecl.}
proc greet(self: TId, x, y: int) {.importobjc: "greet", nodecl.}
proc free(self: TId) {.importobjc: "free", nodecl.}

var g = newGreeter()
g.greet(12, 34)
g.free()

The compiler needs to be told to generate Objective C (command objc) for this to work. The conditional symbol objc is defined when the compiler emits Objective C code.

CodegenDecl pragma

The codegenDecl pragma can be used to directly influence Nimrod's code generator. It receives a format string that determines how the variable or proc is declared in the generated code:

var
  a {.codegenDecl: "$# progmem $#".}: int

proc myinterrupt() {.codegenDecl: "__interrupt $# $#$#".} =
  echo "realistic interrupt handler"

InjectStmt pragma

The injectStmt pragma can be used to inject a statement before every other statement in the current module. It is only supposed to be used for debugging:

{.injectStmt: gcInvariants().}

# ... complex code here that produces crashes ...

LineDir option

The lineDir option can be turned on or off. If turned on the generated C code contains #line directives. This may be helpful for debugging with GDB.

StackTrace option

If the stackTrace option is turned on, the generated C contains code to ensure that proper stack traces are given if the program crashes or an uncaught exception is raised.

LineTrace option

The lineTrace option implies the stackTrace option. If turned on, the generated C contains code to ensure that proper stack traces with line number information are given if the program crashes or an uncaught exception is raised.

Debugger option

The debugger option enables or disables the Embedded Nimrod Debugger. See the documentation of endb for further information.

Breakpoint pragma

The breakpoint pragma was specially added for the sake of debugging with ENDB. See the documentation of endb for further information.

Volatile pragma

The volatile pragma is for variables only. It declares the variable as volatile, whatever that means in C/C++ (its semantics are not well defined in C/C++).

Note: This pragma will not exist for the LLVM backend.

DynlibOverride

By default Nimrod's dynlib pragma causes the compiler to generate GetProcAddress (or their Unix counterparts) calls to bind to a DLL. With the dynlibOverride command line switch this can be prevented and then via --passL the static library can be linked against. For instance, to link statically against Lua this command might work on Linux:

nimrod c --dynlibOverride:lua --passL:liblua.lib program.nim

Nimrod documentation tools

Nimrod provides the doc and doc2 commands to generate HTML documentation from .nim source files. Only exported symbols will appear in the output. For more details see the docgen documentation.

Nimrod idetools integration

Nimrod provides language integration with external IDEs through the idetools command. See the documentation of idetools for further information.

Nimrod interactive mode

The Nimrod compiler supports an interactive mode. This is also known as a REPL (read eval print loop). If Nimrod has been built with the -d:useGnuReadline switch, it uses the GNU readline library for terminal input management. To start Nimrod in interactive mode use the command nimrod i. To quit use the quit() command. To determine whether an input line is an incomplete statement to be continued these rules are used:

1. The line ends with [-+*/\\<>!\?\|%&$@~,;:=#^]\s*$ (operator symbol followed by optional whitespace).
2. The line starts with a space (indentation).
3. The line is within a triple quoted string literal. However, the detection does not work if the line contains more than one """.

Nimrod for embedded systems

The standard library can be avoided to a point where C code generation for 16bit micro controllers is feasible. Use the standalone target (--os:standalone) for a bare bones standard library that lacks any OS features.

To make the compiler output code for a 16bit target use the --cpu:avr target.

For example, to generate code for an AVR processor use this command:

nimrod c --cpu:avr --os:standalone --deadCodeElim:on --genScript x.nim

For the standalone target you need to provide a file panicoverride.nim. See tests/manyloc/standalone/panicoverride.nim for an example implementation.

Nimrod for realtime systems

See the documentation of Nimrod's soft realtime GC for further information.

Debugging with Nimrod

Nimrod comes with its own Embedded Nimrod Debugger. See the documentation of endb for further information.

Optimizing for Nimrod

Nimrod has no separate optimizer, but the C code that is produced is very efficient. Most C compilers have excellent optimizers, so usually it is not needed to optimize one's code. Nimrod has been designed to encourage efficient code: The most readable code in Nimrod is often the most efficient too.

However, sometimes one has to optimize. Do it in the following order:

1. switch off the embedded debugger (it is slow!)
2. turn on the optimizer and turn off runtime checks
3. profile your code to find where the bottlenecks are
4. try to find a better algorithm
5. do low-level optimizations

This section can only help you with the last item.

Optimizing string handling

String assignments are sometimes expensive in Nimrod: They are required to copy the whole string. However, the compiler is often smart enough to not copy strings. Due to the argument passing semantics, strings are never copied when passed to subroutines. The compiler does not copy strings that are a result from a procedure call, because the callee returns a new string anyway. Thus it is efficient to do:

var s = procA() # assignment will not copy the string; procA allocates a new
                # string already

However it is not efficient to do:

var s = varA    # assignment has to copy the whole string into a new buffer!

For let symbols a copy is not always necessary:

let s = varA    # may only copy a pointer if it safe to do so

If you know what you're doing, you can also mark single string (or sequence) objects as shallow:

var s = "abc"
shallow(s) # mark 's' as shallow string
var x = s  # now might not copy the string!

Usage of shallow is always safe once you know the string won't be modified anymore, similar to Ruby's freeze.

The compiler optimizes string case statements: A hashing scheme is used for them if several different string constants are used. So code like this is reasonably efficient:

case normalize(k.key)
of "name": c.name = v
of "displayname": c.displayName = v
of "version": c.version = v
of "os": c.oses = split(v, {';'})
of "cpu": c.cpus = split(v, {';'})
of "authors": c.authors = split(v, {';'})
of "description": c.description = v
of "app":
  case normalize(v)
  of "console": c.app = appConsole
  of "gui": c.app = appGUI
  else: quit(errorStr(p, "expected: console or gui"))
of "license": c.license = UnixToNativePath(k.value)
else: quit(errorStr(p, "unknown variable: " & k.key))

The JavaScript target

Nimrod can also generate JavaScript code. However, the JavaScript code generator is experimental!

Nimrod targets JavaScript 1.5 which is supported by any widely used browser. Since JavaScript does not have a portable means to include another module, Nimrod just generates a long .js file.

Features or modules that the JavaScript platform does not support are not available. This includes:

• manual memory management (alloc, etc.)
• casting and other unsafe operations (cast operator, zeroMem, etc.)
• file management
• most modules of the Standard library
• proper 64 bit integer arithmetic
• unsigned integer arithmetic

However, the modules strutils, math, and times are available! To access the DOM, use the dom module that is only available for the JavaScript platform.

To compile a Nimrod module into a .js file use the js command; the default is a .js file that is supposed to be referenced in an .html file. However, you can also run the code with nodejs:

nimrod js -d:nodejs -r examples/hallo.nim