lldb process save-core will accept anything for the plugin name and silently produce a minidump

[DavidSpickett]

The following does not error:

(lldb) process save-core --plugin-name=notaplugin dump

Modified-memory or stack-memory only corefile created.  This corefile may 
not show library/framework/app binaries on a different system, or when 
those binaries have been updated/modified. Copies are not included
in this corefile.  Use --style full to include all process memory.

But produces a minidump instead:

$ file dump
dump: Mini DuMP crash report, 15 streams, Tue Jun  3 10:51:32 2025, 0 type

1. This command should error, ideally with "and here are the valid plugins you could have chosen".
2. The command should print something to tell you what format of core file was written. Whether you got the plugin name correct or not.

Many people will assume it's the native format of their platform, but it's not, at least not right now. I don't get an ELF core on Linux for example.

[llvmbot]

@llvm/issue-subscribers-lldb

Author: David Spickett (DavidSpickett)

The following does not error: ``` (lldb) process save-core --plugin-name=notaplugin dump

Modified-memory or stack-memory only corefile created. This corefile may
not show library/framework/app binaries on a different system, or when
those binaries have been updated/modified. Copies are not included
in this corefile. Use --style full to include all process memory.

But produces a minidump instead:

$ file dump
dump: Mini DuMP crash report, 15 streams, Tue Jun 3 10:51:32 2025, 0 type

1. This command should error, ideally with "and here are the valid plugins you could have chosen".
2. The command should print something to tell you what format of core file was written. Whether you got the plugin name correct or not.

Many people will assume it's the native format of their platform, but it's not, at least not right now. I don't get an ELF core on Linux for example.

</details>

[Jlalond]

Many people will assume it's the native format of their platform, but it's not, at least not right now. I don't get an ELF core on Linux for example.

I see @da-viper's fix just doesn't run the default if the plugin name is bad, which I agree with. Do we intend to change the default on Linux as well?

[da-viper]

Do we intend to change the default on Linux as well?

@Jlalond It currently checks the elf plugin before trying the minidump. from checking the code (the elf plugin does not support saving core files)

llvm-project/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

Lines 355 to 360 in cf348e8

	// Static methods.
	void ObjectFileELF::Initialize() {
	PluginManager::RegisterPlugin(GetPluginNameStatic(),
	GetPluginDescriptionStatic(), CreateInstance,
	CreateMemoryInstance, GetModuleSpecifications);
	}

[da-viper]

Also I noticed there is no way to know what plugin is available (unless i missed it) without looking through the code. From a user perspective it could be hard to find what plugin they can use.

[DavidSpickett]

I'm not saying we should change the default (and implement elf core saving) but as a user my guess would be that the default is my platform's default.

So that's why it would also be nice to say what format was used for the file.

From a user perspective it could be hard to find what plugin they can use.

In an ideal world:

error: "notaplugin" is not a valid <whatever> plugin, available <whatever> plugins that support writing core files are:
a, b, c

Though for now there's only ever going to be one name in there, minidump.

[Jlalond]

@da-viper as a follow up, we should print the available providers here

[da-viper]

should this be under a different command such as process save-core --list-plugins or appended to the error message as stated above

error: "notaplugin" is not a valid <whatever> plugin, available <whatever> plugins that support writing core files are:

[Jlalond]

I don't think it should be a different command. Imagine @DavidSpickett's hypothetical, I do something like plugin=elf and then get an error that 'elf' is invalid with no further details.

You can only save a Minidump or Mach-O. Would be much more informative.

You can add a different command, but I think the best approach is having the error message denote the available Save-core plugins.

[DavidSpickett]

Adding/improving the error message is strictly better than the current state, and if I had to pick one, I'd take the nicer error message.

Some tools will special case "list" or "help" option values to print the possible values. In fact I talked to someone who thought some tool did that but in fact "list" was just an invalid name and the error was nice enough they didn't notice.

So you could just make the --plugin help text say "to list available plugins, pass --plugin=help`. Special case it if you like but even if you don't, the output is still help-ful.

In theory we could have dynamic help text that looks up the possible values but that's a whole other task that needs more motivating examples (and time) than this one.