Tutorial: Making CLAP plugins

[mystran]

EDIT: Any idea on what's causing the other error? It's something in the definition pluginDescriptor.

What does the problematic line (and preferebly some context around it) look like?

[Majisto]

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Code: Select all (#)

static const clap_plugin_descriptor_t pluginDescriptor = {
	.clap_version = CLAP_VERSION_INIT,
	.id = "nakst.HelloCLAP",
	.name = "HelloCLAP",
	.vendor = "nakst",
	.url = "https://nakst.gitlab.io",
	.manual_url = "https://nakst.gitlab.io",
	.support_url = "https://nakst.gitlab.io",
	.version = "1.0.0",
	.description = "The best audio plugin ever.",

	.features = (const char *[]) {
		CLAP_PLUGIN_FEATURE_INSTRUMENT,
		CLAP_PLUGIN_FEATURE_SYNTHESIZER,
		CLAP_PLUGIN_FEATURE_STEREO,
		NULL,
	},
};

It's in the .features part.

[camsr]

Flexible Array Member ill-defined?

[mystran]

Code: Select all

static const clap_plugin_descriptor_t pluginDescriptor = {
	.clap_version = CLAP_VERSION_INIT,
	.id = "nakst.HelloCLAP",
	.name = "HelloCLAP",
	.vendor = "nakst",
	.url = "https://nakst.gitlab.io",
	.manual_url = "https://nakst.gitlab.io",
	.support_url = "https://nakst.gitlab.io",
	.version = "1.0.0",
	.description = "The best audio plugin ever.",

	.features = (const char *[]) {
		CLAP_PLUGIN_FEATURE_INSTRUMENT,
		CLAP_PLUGIN_FEATURE_SYNTHESIZER,
		CLAP_PLUGIN_FEATURE_STEREO,
		NULL,
	},
};

It's in the .features part.

I'm honestly not sure. It could be the construct is only valid in C(?) even though at least clang does seem to accept it as C++ as well... or it could be a GCC/Clang extension or something like that perhaps?

That said, you should be able to fix this by declaring the array of feature strings as a separate static array and reference that. Not as nice syntax-wise, but produces the same end result.

[syntonica]

It might be an MSVC vs gcc vs clang thing. They've always had these little differences and I've occasionally run into them in the past. It's really annoying and why I don't care for working with other people's code.

[Majisto]

I see. Thanks, guys!

[Mastropiero]

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It might be an MSVC vs gcc vs clang thing. They've always had these little differences and I've occasionally run into them in the past. It's really annoying and why I don't care for working with other people's code.

It's definitely a MSVC vs GCC/CLANG thing. The code builds perfectly on Linux and Mac but it doesn't on Windows.

A valid approach to fix this (without creating any global stuff) is to create a function for the initialization:

Code: Select all (#)

const char **features_init();   //function prototype

const char **features_init() {
  static const char *features[] = {
    CLAP_PLUGIN_FEATURE_INSTRUMENT,
    CLAP_PLUGIN_FEATURE_SYNTHESIZER,
    CLAP_PLUGIN_FEATURE_STEREO,
    NULL,
  };
  return features;
}

static const clap_plugin_descriptor_t pluginDescriptor = {
	.clap_version = CLAP_VERSION_INIT,
	.id = "nakst.HelloCLAP",
	.name = "HelloCLAP",
	.vendor = "nakst",
	.url = "https://nakst.gitlab.io",
	.manual_url = "https://nakst.gitlab.io",
	.support_url = "https://nakst.gitlab.io",
	.version = "1.0.0",
	.description = "The best audio plugin ever.",
	.features = features_init()
};

There are also two minor mistakes in the documentation about how to build the plug-in on Windows:

-The correct flag for DLL making on modern versions of the MSVC compiler is /LD, not /DLL.
-The libraries that have to be added to the compiler command line are user32.lib and gdi32.lib (instead of .dll, as stated on the tutorial).

Thus, the correct command to build the example under Windows should be:

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cl /LD /Zi /std:c++20 plugin.cpp user32.lib gdi32.lib

BTW, hello all. This is my very first post on KVR Audio.

[mystran]

A valid approach to fix this (without creating any global stuff) is to create a function for the initialization:

Constants declared "static" (ie. local to compilation unit) are not what they mean when they say to avoid globals. Function statics are actually theoretically worse, because initialization is on first call and required to be thread-safe.. though here it's all constants so likely to result in the same code either way.

Globals in general, even true globals, aren't all bad.. it's just that if you use them for stuff that's not truly supposed to be global, or where you might need multiple copies later, things tend to get messy.