## Summary I accidentally created a recursively defined variable in this commit [1]. Attempting to build locally gave me the following stack trace after ~15 minutes of making my machine unusable: ``` Traceback (most recent call last): File "/home/thomascoldrick/.local/bin/bst", line 8, in <module> sys.exit(cli()) File "/home/thomascoldrick/.local/lib/python3.5/site-packages/click/core.py", line 722, in __call__ return self.main(*args, **kwargs) File "/home/thomascoldrick/buildstream/buildstream/_frontend/cli.py", line 162, in override_main standalone_mode=standalone_mode, **extra) File "/home/thomascoldrick/.local/lib/python3.5/site-packages/click/core.py", line 697, in main rv = self.invoke(ctx) File "/home/thomascoldrick/.local/lib/python3.5/site-packages/click/core.py", line 1066, in invoke return _process_result(sub_ctx.command.invoke(sub_ctx)) File "/home/thomascoldrick/.local/lib/python3.5/site-packages/click/core.py", line 895, in invoke return ctx.invoke(self.callback, **ctx.params) File "/home/thomascoldrick/.local/lib/python3.5/site-packages/click/core.py", line 535, in invoke return callback(*args, **kwargs) File "/home/thomascoldrick/.local/lib/python3.5/site-packages/click/decorators.py", line 27, in new_func return f(get_current_context().obj, *args, **kwargs) File "/home/thomascoldrick/buildstream/buildstream/_frontend/cli.py", line 330, in build build_all=all_) File "/home/thomascoldrick/buildstream/buildstream/_stream.py", line 184, in build dynamic_plan=True) File "/home/thomascoldrick/buildstream/buildstream/_stream.py", line 871, in _load fetch_subprojects=fetch_subprojects) File "/home/thomascoldrick/buildstream/buildstream/_pipeline.py", line 111, in load fetch_subprojects=fetch_subprojects) File "/home/thomascoldrick/buildstream/buildstream/_project.py", line 321, in load_elements for meta in meta_elements File "/home/thomascoldrick/buildstream/buildstream/_project.py", line 321, in <listcomp> for meta in meta_elements File "/home/thomascoldrick/buildstream/buildstream/element.py", line 926, in _new_from_meta dependency = Element._new_from_meta(meta_dep, artifacts) File "/home/thomascoldrick/buildstream/buildstream/element.py", line 929, in _new_from_meta dependency = Element._new_from_meta(meta_dep, artifacts) File "/home/thomascoldrick/buildstream/buildstream/element.py", line 909, in _new_from_meta element = meta.project.create_element(artifacts, meta, first_pass=meta.first_pass) File "/home/thomascoldrick/buildstream/buildstream/_project.py", line 232, in create_element return self.config.element_factory.create(self._context, self, artifacts, meta) File "/home/thomascoldrick/buildstream/buildstream/_elementfactory.py", line 61, in create element = element_type(context, project, artifacts, meta, default_config) File "/home/thomascoldrick/buildstream/buildstream/element.py", line 248, in __init__ self.__variables = Variables(variables) File "/home/thomascoldrick/buildstream/buildstream/_variables.py", line 48, in __init__ self.variables = self._resolve(node) File "/home/thomascoldrick/buildstream/buildstream/_variables.py", line 148, in _resolve resolved, unmatched = resolve_one(resolved) File "/home/thomascoldrick/buildstream/buildstream/_variables.py", line 134, in resolve_one resolved_var, item_unmatched = self._subst(value, variables) File "/home/thomascoldrick/buildstream/buildstream/_variables.py", line 102, in _subst replacement = re.sub(_VARIABLE_MATCH, subst_callback, string) File "/usr/lib/python3.5/re.py", line 182, in sub return _compile(pattern, flags).sub(repl, string, count) MemoryError ``` However on the CI things failed neatly [2] despite both using 1.1.6 [1] https://gitlab.com/freedesktop-sdk/freedesktop-sdk/commit/9c53d6a5ca16043ea42ac7c54c022e4397bac46b [2] https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/jobs/90954727 ## Steps to reproduce I was reproducing this bug reliably on my machine by running `make runtime export` on the commit linked. However this may not be reproduced on every machine. ## What is the current bug behavior? Buildstream steals all the memory and crashes, sometimes, when recursive variables are defined. ## What is the expected correct behavior? The nice error message which I got in the CI ## Possible fixes Potentially a check for recursion in variables while they're being resolved? ## Other relevant information * BuildStream version affected: 1.1.6 ----