Eval Expr with Expr(:quote) produces segfault

[ssikdar1]

Discovered while doing PR #35363 for Issue #34544.

There are two lines I can come up with that still produce a segfault. (that's a different different code path from the issue mentioned above)

eval(Expr(:quote, Expr(:module, true, :bar, Expr(:quote))))
eval(Expr(:call, :eval, Expr(:quote, Expr(:module, true, :bar, Expr(:quote)))))

Which appear to be related to

julia/src/ast.c

Line 1120 in 60323b6

expr = jl_call_scm_on_ast("julia-bq-macro", jl_exprarg(e, 0), inmodule);

stacktrace:

signal (11): Segmentation fault: 11
in expression starting at none:1
scm_to_julia_ at /Users/ssikdar1/julia/src/ast.c:578
scm_to_julia_ at /Users/ssikdar1/julia/src/ast.c:597
scm_to_julia_ at /Users/ssikdar1/julia/src/ast.c:579
scm_to_julia_ at /Users/ssikdar1/julia/src/ast.c:597
scm_to_julia at /Users/ssikdar1/julia/src/ast.c:455
jl_call_scm_on_ast at /Users/ssikdar1/julia/src/ast.c:961 [inlined]
jl_expand_macros at /Users/ssikdar1/julia/src/ast.c:1120
jl_expand_macros at /Users/ssikdar1/julia/src/ast.c:1190
jl_expand_with_loc_warn at /Users/ssikdar1/julia/src/ast.c:1245
jl_toplevel_eval_flex at /Users/ssikdar1/julia/src/toplevel.c:633
jl_toplevel_eval at /Users/ssikdar1/julia/src/toplevel.c:822 [inlined]
jl_toplevel_eval_in at /Users/ssikdar1/julia/src/toplevel.c:845

I tried adding a display to julia-bq-expand- in src/macroexpand.scm

+++ b/src/macroexpand.scm
@@ -15,6 +15,10 @@
               (loop (cdr lst) (cons nxt out)))))))
 
 (define (julia-bq-expand- x d)
+  (display "\n x: ")
+  (display x)
+  (display "\n d: ")
+  (display d)

which outputs:

julia> eval(Expr(:quote, Expr(:module, true, :bar, Expr(:quote))))

 x: (module (true) bar (quote))

trying this statement in the julia --lisp returns a compilation error:

> (module (true) bar (quote))
type error: car: expected cons, got ()
#0 (compile-in [(2 loadg 0 call 1 loadg 0 loadg 0 argc)
	     #table(true 1  bar 2  module 0) 3 () 7]
	    (()) #f (quote))
#1 (compile-arglist/lambda
 (quote))
#2 (compile-arglist [(2 loadg 0 call 1 loadg 0 loadg 0 argc)
		  #table(true 1  bar 2  module 0) 3 () 7]
		 (()) ((true) bar (quote)))
#3 (compile-app [(2 loadg 0 call 1 loadg 0 loadg 0 argc)
	      #table(true 1  bar 2  module 0) 3 () 7]
	     (()) #t (module (true) bar (quote)))
#4 (compile-f- () (lambda ()
		 (module (true) bar (quote))))
#5 (lambda #fn("7000r0e0~\x7f42;" [compile-f-] [() (lambda ()
						  (module (true) bar (quote)))])
  #fn("5000r2|;" []))
#6 (eval (module (true) bar (quote)))

So it seems the value getting passed to julia-bq-macro is incorrect?

[JeffBezanson]

trying this statement in the julia --lisp returns a compilation error:

> (module (true) bar (quote))

That isn't lisp code; it's a julia AST written as lisp data, so it cannot be evaluated as lisp.

[JeffBezanson]

scm_to_julia_ at /Users/ssikdar1/julia/src/ast.c:578

It looks like this could be fixed by adding a check here that iscons(e).