(const c-string) as result type breaks with NULL

[Vasilij Schneidermann]

I'm writing bindings to a library which uses const on both string argument and return types. If I declare a foreign function returning NULL to have (const c-string) as return type, I get a segmentation violation, c-string as return type however returns #f as expected.

Minimal repro:

(import chicken scheme foreign)

#> static const char* test() { return NULL; } <#

(define test (foreign-lambda c-string "test"))
(define test2 (foreign-lambda (const c-string) "test"))

(test) ;=> #f
(test2) ;=> segfault

[Vasilij Schneidermann]

FWIW, ​the C4 patch resolves the issue for me.

[evhan]

Fixed with a0bb345 and c3393980.