What are Node.js "Linked" modules?

@bnoordhuis

When I was going through the source code, I found this in node.cc,

// "Linked" modules are included as part of the node project.
// Like builtins they are registered *before* node::Init runs.
mp->nm_flags = NM_F_LINKED;

Does anybody know what "Linked" modules are? @bnoordhuis maybe?

cc @addaleax

It's probably this in the build script:

parser.add_option("--link-module",
    action="append",
    dest="linked_module",
    help="Path to a JS file to be bundled in the binary as a builtin."
         "This module will be referenced by path without extension."
         "e.g. /root/x/y.js will be referenced via require('root/x/y')."
         "Can be used multiple times")

@mscdex

@mscdex That’s something different. The linked modules the C++ source is talking about would be native modules that are compiled into (or LD_PRELOLADed into?) the node executable itself, not JS code.

Well, that's not confusing ;-)

The configure switch is for baking third-party JS source code into the binary, NM_F_LINKED is for bundling add-ons into the binary. Unfortunate name clash, yes.

@bnoordhuis

@bnoordhuis Is there anybody who uses that feature? Would documenting it be a good idea?

I assume so, at least at the time, otherwise why bother making a pull request? Both features where requested and implemented by non-collaborators.

Documenting it: no reason not to, I suppose.

Hi I'd like to work on this. This is my first time working on open source and I was wondering which part of the documentation this should go into, and generally the relevant parts of the source I should be looking at.

@bnoordhuis

I guess it should go somewhere in https://nodejs.org/api/modules.html (source here)?

As mentioned above, for the Native module you probably want to start here:

node/src/node.cc

Lines 2595 to 2599 in 4359a93

    
           // "Linked" modules are included as part of the node project. 
        
           // Like builtins they are registered *before* node::Init runs. 
        
           mp->nm_flags = NM_F_LINKED; 
        
           mp->nm_link = modlist_linked; 
        
           modlist_linked = mp;

For the js module you probably want to start here:

node/configure

Lines 152 to 158 in 201ecef

    
           parser.add_option("--link-module", 
        
               action="append", 
        
               dest="linked_module", 
        
               help="Path to a JS file to be bundled in the binary as a builtin." 
        
                    "This module will be referenced by path without extension." 
        
                    "e.g. /root/x/y.js will be referenced via require('root/x/y')." 
        
                    "Can be used multiple times")

@bnoordhuis are the two features functionally identical, except for the fact that one is for native addons and one is for js addons?

@gibfahn

Awesome, thanks for the tips @gibfahn I'll look into it.

doc: add builtin module in building.md

Reopen since the OP is asking about native modules and they are still not documented. Should be fixed by #19112

@joyeecheung

Sounds like this was addressed by @joyeecheung above. Closing.

doc: add builtin module in building.md

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What are Node.js "Linked" modules? #12516

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	// "Linked" modules are included as part of the node project.
	// Like builtins they are registered before node::Init runs.
	mp->nm_flags = NM_F_LINKED;
	mp->nm_link = modlist_linked;
	modlist_linked = mp;

	parser.add_option("--link-module",
	action="append",
	dest="linked_module",
	help="Path to a JS file to be bundled in the binary as a builtin."
	"This module will be referenced by path without extension."
	"e.g. /root/x/y.js will be referenced via require('root/x/y')."
	"Can be used multiple times")

What are Node.js "Linked" modules? #12516

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mscdex commented on Apr 19, 2017

addaleax commented on Apr 19, 2017

mscdex commented on Apr 19, 2017

bnoordhuis commented on Apr 19, 2017

addaleax commented on Apr 19, 2017

bnoordhuis commented on Apr 19, 2017

snggeng commented on Oct 29, 2017

gibfahn commented on Oct 29, 2017

snggeng commented on Oct 30, 2017

6 remaining items

joyeecheung commented on Mar 4, 2018

apapirovski commented on Apr 14, 2018

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