cgo aborts translation for unknown type pointers #126
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That seems a bit kludgy - the Size is coming back as 0 on the struct, not something referencing it, and so making it a void pointer is actually technically wrong (however, for most intents and purposes, it works until you attempt to dereference it). My solution which needs to be better verified was to make it a 0 byte opaque object, but what it needs to be really is a "Unknown size" opaque object, and checks need to be made that it's never dereferenced through that unknown-size object, and that the object is never copied inside of go code. |
Agreed, cgo already renders some types using Opaque() which turns unknown types into
a byte array of fixed size. Maybe we can just treat types with invalid byte sizes as
0-length byte arrays? It seems Go wouldn't be able to copy the object if this is the
case.
Here's a patch which works for me for when consuming libmysql.
diff -r 1d9d926b1aa7 src/cmd/cgo/gcc.go
--- a/src/cmd/cgo/gcc.go Thu Nov 12 23:38:48 2009 -0800
+++ b/src/cmd/cgo/gcc.go Fri Nov 13 10:01:45 2009 -0800
@@ -315,11 +315,15 @@
t.Size = dtype.Size();
t.Align = -1;
t.C = dtype.Common().Name;
+ c.m[dtype] = t;
+
if t.Size < 0 {
- fatal("dwarf.Type %s reports unknown size", dtype)
+ // Treat unsized types as [0]byte
+ t.Size = 0;
+ t.Go = c.Opaque(0);
+ return t;
}
- c.m[dtype] = t;
switch dt := dtype.(type) {
default:
fatal("unexpected type: %s", dtype)
|
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Issue #161 has been merged into this issue. |
|
Owner changed to r...@golang.org. |
|
This issue was closed by revision b30f753. Status changed to Fixed. Merged into issue #-. |
This issue was closed.
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by eden.li:
What steps will reproduce the problem? $ cat > empty.go <<EOF package main /* struct st_dne; typedef struct st_dne dne; typedef struct { dne *a; } empty; */ import "C" var a C.empty EOF $ cgo empty.go; echo $? dwarf.Type dne reports unknown size. 2 What is the expected output? What do you see instead? Some libraries (e.g. libmysql) define empty structs similar to the one above. cgo should translate these into void pointers instead of aborting. What is your $GOOS? $GOARCH? darwin, 386 Which revision are you sync'ed to? (hg log -l 1) 4018:bbc290c53f85 (Thu Nov 12 16:12:28 2009 -0800) Please provide any additional information below. This patch appears to fix the problem. diff -r bbc290c53f85 src/cmd/cgo/gcc.go --- a/src/cmd/cgo/gcc.go Thu Nov 12 16:12:28 2009 -0800 +++ b/src/cmd/cgo/gcc.go Thu Nov 12 17:13:47 2009 -0800 @@ -420,6 +420,13 @@ break; } + // Translate unknown type pointers as unsafe.Pointer + if dt.Type.Size() < 0 { + t.Go = c.unsafePointer; + t.C = "void*"; + break; + } + gt := &ast.StarExpr{}; t.Go = gt; // publish before recursive call sub := c.Type(dt.Type);The text was updated successfully, but these errors were encountered: