Hi all, I discovered that running code which contains FFI macro calls through the interpreter will cause a segfault. This happens because these macros call procedures from the compiler directly.
I don't know why this is not an issue in CHICKEN 4; it seems that the module itself can be imported, but the macros are not defined by it in the interpreter? I would really love a clarification of this, so that we're sure master doesn't need a similar patch. It calls some procedures which are prefixed ##compiler#, so I suppose the same problem would exist there if one were able to expand these macros in the interpreter. I tried to move foreign-type->scrutiny-type from support.scm into chicken-ffi-syntax.scm, but it turns out the comment is misleading: foreign-type->scrutiny-type is used in the scrutinizer too, so we can't simply move it. Besides, foreign-type->scrutiny-type calls final-foreign-type, which uses lookup-foreign-type, which consults foreign-type-table and so on and so on, so if we wanted to move it we'd have to do a pretty large restructuring (if possible at all). So instead, I decided it would be better if the macros themselves would simply raise a syntax error upon expansion. Alternatively, we could try to raise an error in chicken.foreign.import.scm when an attempt is made to load it, but I think the approach of letting the macros themselves bail out is somewhat cleaner. A disadvantage of this is that you can't expand the macro in the interpreter to see what kind of code it generates. Another approach would be to stub out the helper functions so they return a fake value, but that would be even more confusing because the code wouldn't be representative for the actual code it expands to. Cheers, Peter
From e02b684150b75e526b22d0857e0dbc0492958611 Mon Sep 17 00:00:00 2001
From: Peter Bex <pe...@more-magic.net>
Date: Sun, 12 Nov 2017 14:03:33 +0100
Subject: [PATCH] Avoid expanding to unbound procedures in FFI macros.
These macros call procedures that are defined inside the compiler
only. This will result in an "unbound variable" error in DEBUGBUILD
CHICKENs, and a segfault(!) in non-DEBUGBUILDs.
So, we check to see if the macro expander is running inside the
compiler and emit an error if that's not the case.
---
chicken-ffi-syntax.scm | 46 ++++++++++++++++++++++++++++------------------
support.scm | 4 ++--
2 files changed, 30 insertions(+), 20 deletions(-)
diff --git a/chicken-ffi-syntax.scm b/chicken-ffi-syntax.scm
index 0b3008c0..255c9c93 100644
--- a/chicken-ffi-syntax.scm
+++ b/chicken-ffi-syntax.scm
@@ -31,9 +31,6 @@
(disable-interrupts)
(fixnum))
-;; IMPORTANT: These macros expand directly into fully qualified names
-;; from the "chicken.compiler.c-backend" and "chicken.compiler.support" modules.
-
#+(not debugbuild)
(declare
(no-bound-checks)
@@ -42,6 +39,8 @@
(import chicken.base
chicken.format
chicken.internal
+ chicken.platform
+ chicken.syntax
chicken.string)
(include "common-declarations.scm")
@@ -50,10 +49,21 @@
(define ##sys#chicken-ffi-macro-environment
(let ((me0 (##sys#macro-environment)))
+;; IMPORTANT: These macros directly call fully qualified names from
+;; the "chicken.compiler.c-backend" and "chicken.compiler.support"
+;; modules. These are unbound in the interpreter, so check first:
+(define (compiler-only-er-transformer transformer)
+ (##sys#er-transformer
+ (lambda (form r c)
+ (if (feature? 'compiling)
+ (transformer form r c)
+ (syntax-error
+ (car form) "The FFI is not supported in interpreted mode")))))
+
(##sys#extend-macro-environment
'define-external
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(let* ((form (cdr form))
(quals (and (pair? form) (string? (car form))))
@@ -90,7 +100,7 @@
(##sys#extend-macro-environment
'location
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (x r c)
(##sys#check-syntax 'location x '(location _))
`(##core#location ,(cadr x)))))
@@ -98,7 +108,7 @@
(##sys#extend-macro-environment
'define-location
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'define-location form '(_ variable _ . #(_ 0 1)))
(let ((var (cadr form))
@@ -115,7 +125,7 @@
(##sys#extend-macro-environment
'let-location
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'let-location form '(_ #((variable _ . #(_ 0 1)) 0) . _))
(let* ((bindings (cadr form))
@@ -151,7 +161,7 @@
(##sys#extend-macro-environment
'foreign-code
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-code form '(_ . #(string 0)))
(let ([tmp (gensym 'code_)])
@@ -166,7 +176,7 @@
(##sys#extend-macro-environment
'foreign-value
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-value form '(_ _ _))
(let ((tmp (gensym "code_"))
@@ -192,7 +202,7 @@
(##sys#extend-macro-environment
'foreign-declare
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-declare form '(_ . #(string 0)))
`(##core#declare (foreign-declare ,@(cdr form))))))
@@ -203,7 +213,7 @@
(##sys#extend-macro-environment
'define-foreign-type
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'define-foreign-type form '(_ symbol _ . #(_ 0 2)))
`(##core#define-foreign-type ,@(cdr form)))))
@@ -211,7 +221,7 @@
(##sys#extend-macro-environment
'define-foreign-variable
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'define-foreign-variable form '(_ symbol _ . #(string 0 1)))
`(##core#define-foreign-variable ,@(cdr form)))))
@@ -219,7 +229,7 @@
(##sys#extend-macro-environment
'foreign-primitive
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-primitive form '(_ _ . _))
(let* ((hasrtype (and (pair? (cddr form)) (not (string? (caddr form)))))
@@ -238,7 +248,7 @@
(##sys#extend-macro-environment
'foreign-lambda
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-lambda form '(_ _ _ . _))
`(##core#the
@@ -252,7 +262,7 @@
(##sys#extend-macro-environment
'foreign-lambda*
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-lambda* form '(_ _ _ _ . _))
`(##core#the
@@ -269,7 +279,7 @@
(##sys#extend-macro-environment
'foreign-safe-lambda
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-safe-lambda form '(_ _ _ . _))
`(##core#the
@@ -283,7 +293,7 @@
(##sys#extend-macro-environment
'foreign-safe-lambda*
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-safe-lambda* form '(_ _ _ _ . _))
`(##core#the
@@ -298,7 +308,7 @@
(##sys#extend-macro-environment
'foreign-type-size
'()
- (##sys#er-transformer
+ (compiler-only-er-transformer
(lambda (form r c)
(##sys#check-syntax 'foreign-type-size form '(_ _))
(let* ((t (chicken.syntax#strip-syntax (cadr form)))
diff --git a/support.scm b/support.scm
index 905f7ae8..c99af103 100644
--- a/support.scm
+++ b/support.scm
@@ -1144,7 +1144,7 @@
(list argconv a) )
a) )
-(define (final-foreign-type t0) ; Used only in compiler.scm
+(define (final-foreign-type t0) ; Used here and in compiler.scm
(follow-without-loop
t0
(lambda (t next)
@@ -1254,7 +1254,7 @@
;;; Translate foreign-type into scrutinizer type:
-;; Used only in chicken-ffi-syntax.scm; can we move it there?
+;; Used in chicken-ffi-syntax.scm and scrutinizer.scm
(define (foreign-type->scrutiny-type t mode) ; MODE = 'arg | 'result
(let ((ft (final-foreign-type t)))
(case ft
--
2.11.0
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