General issue [cpp] Bug when using Macro in query

[dragoudin]

Description of the issue

• I have a cpp query very simple

import cpp

from Macro m
where
  ( 

• I use vscode extension and I have an error

And error text is

Preprocessor::PreprocessorDirective.extends incompatible with @using \/ @stmt_constexpr_if \/ @stmt_range_based_for \/ @stmt_switch \/ @stmt_for \/ @stmt_end_test_while \/ @stmt_block \/ @stmt_while \/ @stmt_if \/ @isvolatile \/ @isvoid \/ @isunsigned \/ @issigned \/ @isscalar \/ @isrvaluereference \/ @isreference \/ @ispointer \/ @isobject \/ @ismemberpointer \/ @ismemberobjectpointer \/ @ismemberfunctionpointer \/ @islvaluereference \/ @isintegral \/ @isfundamental \/ @isfloatingpoint \/ @isconst \/ @iscompound \/ @iscompletetype \/ @isarithmetic \/ @arrayextent \/ @arrayrank \/ @isarray \/ @ispointerinterconvertiblebaseof \/ @islayoutcompatible \/ @isfunction \/ @issame \/ @blockassignexpr \/ @builtinshuffle \/ @builtinbitcast \/ @hasuniqueobjectrepresentations \/ @isaggregate \/ @isassignable \/ @temp_init \/ @co_yield \/ @co_await \/ @spaceshipexpr \/ @builtincomplex \/ @builtinconvertvector \/ @vec_fill \/ @builtinaddressof \/ @builtinchooseexpr \/ @builtinshufflevector \/ @noexceptexpr \/ @isfinalexpr \/ @isvalueclassexpr \/ @issimplevalueclassexpr \/ ...(227 other disjuncts) in context

• When I run the command line, I have the following message

Compiling query plan for C:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\export_macros.ql.
ERROR: Preprocessor::PreprocessorDirective.extends incompatible with @using \/ @stmt_constexpr_if \/ @stmt_range_based_for \/ @stmt_switch \/ @stmt_for \/ @stmt_end_test_while \/ @stmt_block \/ @stmt_while \/ @stmt_if \/ @isvolatile \/ @isvoid \/ @isunsigned \/ @issigned \/ @isscalar \/ @isrvaluereference \/ @isreference \/ @ispointer \/ @isobject \/ @ismemberpointer \/ @ismemberobjectpointer \/ @ismemberfunctionpointer \/ @islvaluereference \/ @isintegral \/ @isfundamental \/ @isfloatingpoint \/ @isconst \/ @iscompound \/ @iscompletetype \/ @isarithmetic \/ @arrayextent \/ @arrayrank \/ @isarray \/ @ispointerinterconvertiblebaseof \/ @islayoutcompatible \/ @isfunction \/ @issame \/ @blockassignexpr \/ @builtinshuffle \/ @builtinbitcast \/ @hasuniqueobjectrepresentations \/ @isaggregate \/ @isassignable \/ @temp_init \/ @co_yield \/ @co_await \/ @spaceshipexpr \/ @builtincomplex \/ @builtinconvertvector \/ @vec_fill \/ @builtinaddressof \/ @builtinchooseexpr \/ @builtinshufflevector \/ @noexceptexpr \/ @isfinalexpr \/ @isvalueclassexpr \/ @issimplevalueclassexpr \/ ...(219 other disjuncts) in context 
(C:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\export_macros.ql:4,6-13)

I use latest version of codeql 2.16.1 (this query was working fine few months ago)

[aeisenberg]

Can you please share the full query?

[dragoudin]

Here is my full query (very simple) and before to run the codeql query on vscode there is a red message.

import cpp

from Macro m
where not m.getFile().getAbsolutePath().regexpMatch(".(START|STOP)SEC.")
select m.getLocation(), m.getName(), m.getBody(), m.getParentScope(), m.getFile().getBaseName()

It seems the problem comes from the Macro class as I see no problem as my request is very simple.
I use codeql version 2.16.1

[aeisenberg]

Thanks for the full query. I can reproduce with a simpler example.

import cpp

from Macro m
select m.getParentScope()

Let me discuss with the compiler team.

[intrigus-lgtm]

Isn't the error message pretty much telling you that Macro.getParentScope() can never have a result in a convoluted way?
There is no case for Macro here:

codeql/cpp/ql/lib/semmle/code/cpp/Element.qll

Lines 126 to 169 in 92bd550

	/**
	* Gets the parent scope of this `Element`, if any.
	* A scope is a `Type` (`Class` / `Enum`), a `Namespace`, a `BlockStmt`, a `Function`,
	* or certain kinds of `Statement`.
	*/
	Element getParentScope() {
	// result instanceof class
	exists(Declaration m |
	m = this and
	result = m.getDeclaringType() and
	not this instanceof EnumConstant
	)
	or
	exists(TemplateClass tc | this = tc.getATemplateArgument() and result = tc)
	or
	// result instanceof namespace
	exists(Namespace n | result = n and n.getADeclaration() = this)
	or
	exists(FriendDecl d, Namespace n | this = d and n.getADeclaration() = d and result = n)
	or
	exists(Namespace n | this = n and result = n.getParentNamespace())
	or
	// result instanceof stmt
	exists(LocalVariable v |
	this = v and
	exists(DeclStmt ds | ds.getADeclaration() = v and result = ds.getParent())
	)
	or
	exists(Parameter p | this = p and result = p.getFunction())
	or
	exists(GlobalVariable g, Namespace n | this = g and n.getADeclaration() = g and result = n)
	or
	exists(EnumConstant e | this = e and result = e.getDeclaringEnum())
	or
	// result instanceof block|function
	exists(BlockStmt b | this = b and blockscope(unresolveElement(b), unresolveElement(result)))
	or
	exists(TemplateFunction tf | this = tf.getATemplateArgument() and result = tf)
	or
	// result instanceof stmt
	exists(ControlStructure s | this = s and result = s.getParent())
	or
	using_container(unresolveElement(result), underlyingElement(this))
	}

Afaik when the compiler can statically determine that Macro.getParentScope() can never have a result it fails with this error message.

[aeisenberg]

Thanks, @intrigus-lgtm. That's exactly correct. I misinterpreted the error message (and was just about to post that). The fact that there is an error is correct. However, it is not particularly user friendly. We are thinking of ways of making this better to use.

In the meantime, simply remove the m.getParentScope() clause and your query will compile.

[dragoudin]

I removed the call m.getParentScope() and my query works fine

That's a good workaround as this info is useless for my case, but the error message in vscode indicates the macro class instead of the wrong function m.getParentScope()
Thanks

[aeisenberg]

Thanks for confirming your workaround. We're now tracking internally this via an issue to improve the error message.