runtime: garbage collector found invalid heap pointer

[Thinkofname]

runtime: garbage collector found invalid heap pointer *(0xc2080b9a10+0x20)=0x6 s=nil
fatal error: invalid heap pointer

runtime stack:
runtime.throw(0x100f463)
    /home/matt/go/src/runtime/panic.go:491 +0xad fp=0x7fd222ffc900 sp=0x7fd222ffc8d0
scanblock(0xc2080b9a10, 0x28, 0x988a40)
    /home/matt/go/src/runtime/mgc0.c:381 +0x551 fp=0x7fd222ffca40 sp=0x7fd222ffc900
scanframe(0x7fd222ffcb48, 0x0, 0x1)
    /home/matt/go/src/runtime/mgc0.c:743 +0x1c2 fp=0x7fd222ffcab0 sp=0x7fd222ffca40
runtime.gentraceback(0x463cd5, 0xc2080b99c8, 0x0, 0xc208000120, 0x0, 0x0, 0x7fffffff, 0x7fd222ffcbf8, 0x0, 0x0, ...)
    /home/matt/go/src/runtime/traceback.go:311 +0x7a8 fp=0x7fd222ffcba0 sp=0x7fd222ffcab0
scanstack(0xc208000120)
    /home/matt/go/src/runtime/mgc0.c:780 +0x21c fp=0x7fd222ffcc10 sp=0x7fd222ffcba0
markroot(0xc208012000, 0x5)
    /home/matt/go/src/runtime/mgc0.c:556 +0xe7 fp=0x7fd222ffcc70 sp=0x7fd222ffcc10
runtime.parfordo(0xc208012000)
    /home/matt/go/src/runtime/parfor.c:91 +0x13b fp=0x7fd222ffccf0 sp=0x7fd222ffcc70
runtime.gchelper()
    /home/matt/go/src/runtime/mgc0.c:1188 +0x4a fp=0x7fd222ffcd18 sp=0x7fd222ffccf0
stopm()
    /home/matt/go/src/runtime/proc.c:1181 +0x158 fp=0x7fd222ffcd38 sp=0x7fd222ffcd18
gcstopm()
    /home/matt/go/src/runtime/proc.c:1351 +0xed fp=0x7fd222ffcd60 sp=0x7fd222ffcd38
schedule()
    /home/matt/go/src/runtime/proc.c:1551 +0x9b fp=0x7fd222ffcd90 sp=0x7fd222ffcd60
runtime.gosched_m(0xc208db4c60)
    /home/matt/go/src/runtime/proc.c:1674 +0xac fp=0x7fd222ffcdb0 sp=0x7fd222ffcd90
runtime.newstack()
    /home/matt/go/src/runtime/stack.c:776 +0x4fa fp=0x7fd222ffce60 sp=0x7fd222ffcdb0
runtime.morestack()
    /home/matt/go/src/runtime/asm_amd64.s:324 +0x7e fp=0x7fd222ffce68 sp=0x7fd222ffce60

goroutine 1 [runnable, locked to thread]:
runtime.cgocall_errno(0x44f0a0, 0xc2080b9a10, 0x2000000000)
    /home/matt/go/src/runtime/cgocall.go:130 +0xf5 fp=0xc2080b99f0 sp=0xc2080b99c8
github.com/go-gl/gl/v2.1/gl._Cfunc_glowVertexAttribPointer(0x7fd232b7cc40, 0x300000001, 0x100001401, 0x9, 0x6)
    github.com/go-gl/gl/v2.1/gl/_obj/_cgo_gotypes.go:20441 +0x45 fp=0xc2080b9a10 sp=0xc2080b99f0
github.com/go-gl/gl/v2.1/gl.VertexAttribPointer(0x300000001, 0x100001401, 0x1a200000009, 0x6)
    /home/matt/gopath/src/github.com/go-gl/gl/v2.1/gl/package.go:26335 +0x69 fp=0xc2080b9a40 sp=0xc2080b9a10

This randomly happens when calling gl.VertexAttribPointer with an offset other than zero, in this case 6. I'm assuming its because Go expects unsafe.Pointer to be pointing to a valid address instead of an offset. Any way to fix/work around?

go version go1.4.2 linux/amd64

[dmitshur]

Thanks for reporting this issue. This looks like a valid problem that we'll need to fix.

I've never run into it myself because I never tried non-zero pointer offsets.

[Thinkofname]

My understanding of C is limited but something like this seems to work:

diff --git a/v2.1/gl/package.go b/v2.1/gl/package.go
index 5656428..dd2f17d 100644
--- a/v2.1/gl/package.go
+++ b/v2.1/gl/package.go
@@ -10266,6 +10266,9 @@ package gl
 // static void  glowVertexAttribPointer(GPVERTEXATTRIBPOINTER fnptr, GLuint  index, GLint  size, GLenum  type, GLboolean  normalized, GLsizei  stride, const void * pointer) {
 //   (*fnptr)(index, size, type, normalized, stride, pointer);
 // }
+// static void  glowVertexAttribPointerOffset(GPVERTEXATTRIBPOINTER fnptr, GLuint  index, GLint  size, GLenum  type, GLboolean  normalized, GLsizei  stride, intptr_t pointer) {
+//   (*fnptr)(index, size, type, normalized, stride, (void *) pointer);
+// }
 // static void  glowVertexAttribPointerARB(GPVERTEXATTRIBPOINTERARB fnptr, GLuint  index, GLint  size, GLenum  type, GLboolean  normalized, GLsizei  stride, const void * pointer) {
 //   (*fnptr)(index, size, type, normalized, stride, pointer);
 // }
@@ -26334,6 +26337,10 @@ func VertexAttribParameteriAMD(index uint32, pname uint32, param int32) {
 func VertexAttribPointer(index uint32, size int32, xtype uint32, normalized bool, stride int32, pointer unsafe.Pointer) {
    C.glowVertexAttribPointer(gpVertexAttribPointer, (C.GLuint)(index), (C.GLint)(size), (C.GLenum)(xtype), (C.GLboolean)(boolToInt(normalized)), (C.GLsizei)(stride), pointer)
 }
+func VertexAttribPointerOffset(index uint32, size int32, xtype uint32, normalized bool, stride int32, pointer uintptr) {
+   C.glowVertexAttribPointerOffset(gpVertexAttribPointer, (C.GLuint)(index), (C.GLint)(size), (C.GLenum)(xtype), (C.GLboolean)(boolToInt(normalized)), (C.GLsizei)(stride), (C.intptr_t)(pointer))
+}
+
 func VertexAttribPointerARB(index uint32, size int32, xtype uint32, normalized bool, stride int32, pointer unsafe.Pointer) {
    C.glowVertexAttribPointerARB(gpVertexAttribPointerARB, (C.GLuint)(index), (C.GLint)(size), (C.GLenum)(xtype), (C.GLboolean)(boolToInt(normalized)), (C.GLsizei)(stride), pointer)
 }

[pwaller]

Ping.

I guess these issues have since been dealt with, is that true @shurcooL?

[dmitshur]

As far as I know, there was no action take to deal with this.

I think I missed @Thinkofname's reply and forgot about this issue.

To resolve it, we'll need a reproduce case to confirm it's still an issue, and then try the fix @Thinkofname suggested.

[errcw]

Ultimately a duplicate of #80, and the relevant discussion is there, so I'm going to close this issue.