Comments (6)
dmitshur
commented on July 21, 2024
use-of-uninitialized-value
Is it possible to see which lines of code, or variable names it's referring to?
from example.
zzz125
commented on July 21, 2024
I can't test it right now.
For me its a non-issue currently, but i think it could be a bug or something.
Maybe someone else can test this in future.
from example.
dmitshur
commented on July 21, 2024
It looks like -msan flag is Linux only:
https://github.com/golang/go/blob/go1.6.2/src/runtime/msan/msan.go#L5
So someone with Linux would need to look into it.
from example.
pwaller
commented on July 21, 2024
Tested on Ubuntu 16.04.
I can reproduce this here. Here is a go tool objdump run on the binary. dump.gz
==31406==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x6ff345 (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x6ff345)
#1 0x6ed1dd (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x6ed1dd)
#2 0x71b91f (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x71b91f)
#3 0x4f06cf (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x4f06cf)
SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x6ff345)
#0 is the msan crash thunk. #1 is glfwInit, #2 is _cgo_4c81a0848e0b_Cfunc_glfwInit but the stack return address appears to be one byte short of an instruction.
:0 0x6ed19f 0f842c020000 JE 0x6ed3d1
:0 0x6ed1a5 41bf01000000 MOVL $0x1, R15
:0 0x6ed1ab 85c0 TESTL AX, AX
:0 0x6ed1ad 0f85fe010000 JNE 0x6ed3b1
:0 0x6ed1b3 4c8d256e398902 LEAQ 0x289396e(IP), R12
:0 0x6ed1ba 31f6 XORL SI, SI
:0 0x6ed1bc baa80d0000 MOVL $0xda8, DX
:0 0x6ed1c1 4c89e7 MOVQ R12, DI
:0 0x6ed1c4 e84790d7ff CALL __msan_memset(SB)
:0 0x6ed1c9 4c8b2d908d3e00 MOVQ 0x3e8d90(IP), R13
:0 0x6ed1d0 6441c7450000000000 FS MOVL $0x0, FS:0(R13)
:0 0x6ed1d9 e8a2db0000 CALL _glfwPlatformInit(SB)
:0 0x6ed1de 64418b4d00 FS MOVL FS:0(R13), CX
:0 0x6ed1e3 85c9 TESTL CX, CX
:0 0x6ed1e5 740a JE 0x6ed1f1
:0 0x6ed1e7 f7d1 NOTL CX
:0 0x6ed1e9 21c1 ANDL AX, CX
:0 0x6ed1eb 0f84e5010000 JE 0x6ed3d6
:0 0x6ed1f1 85c0 TESTL AX, AX
:0 0x6ed1f3 0f8463010000 JE 0x6ed35c
:0 0x6ed1f9 488b05f88d3e00 MOVQ 0x3e8df8(IP), AX
Unfortunately, I can't reproduce this with plain-old-c. In a subdirectory of the cube example I did the following, compiling glfw in the same way that go does, from sources shipped with the go glfw package.
clang-3.8 \
-fsanitize=address \
-D_GLFW_X11 \
-I \
../../../glfw/v3.2/glfw/glfw/include/GLFW/ \
main.c \
../../../glfw/v3.2/glfw/glfw/src/context.c \
../../../glfw/v3.2/glfw/glfw/src/init.c \
../../../glfw/v3.2/glfw/glfw/src/input.c \
../../../glfw/v3.2/glfw/glfw/src/monitor.c \
../../../glfw/v3.2/glfw/glfw/src/vulkan.c \
../../../glfw/v3.2/glfw/glfw/src/window.c \
../../../glfw/v3.2/glfw/glfw/src/x11_init.c \
../../../glfw/v3.2/glfw/glfw/src/x11_monitor.c \
../../../glfw/v3.2/glfw/glfw/src/x11_window.c \
../../../glfw/v3.2/glfw/glfw/src/glx_context.c \
../../../glfw/v3.2/glfw/glfw/src/linux_joystick.c \
../../../glfw/v3.2/glfw/glfw/src/posix_time.c \
../../../glfw/v3.2/glfw/glfw/src/posix_tls.c \
../../../glfw/v3.2/glfw/glfw/src/xkb_unicode.c \
../../../glfw/v3.2/glfw/glfw/src/egl_context.c \
-lGL \
-lX11 \
-lXrandr \
-lXxf86vm \
-lXi \
-lXcursor \
-lm \
-lXinerama \
-ldl \
-lrt \
-pthread
With a main.c:
#include <glfw3.h>
#include <stdio.h>
int main(int argc, char const *argv[]) {
glfwInit();
return 0;
}
So, the long and short of it is, I'm not sure what is triggering this.
from example.
pwaller
commented on July 21, 2024
My first attempt at using gdb didn't get anywhere and just resulted in segfaults. But for some reason it's working now. I was able to hit it while single stepping.
Thread 1 "gl41core-cube" hit Breakpoint 1, glfwInit () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/init.c:122
122 if (_glfwInitialized)
(gdb) step
125 memset(&_glfw, 0, sizeof(_glfw));
(gdb)
127 if (!_glfwPlatformInit())
(gdb)
_glfwPlatformInit () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:748
748 _glfw.x11.cursor = createHiddenCursor();
(gdb)
createHiddenCursor () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:625
625 unsigned char pixels[16 * 16 * 4];
(gdb)
_glfwPlatformInit () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:745
745 if (!initExtensions())
(gdb)
initExtensions () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:745
745 if (!initExtensions())
(gdb)
createKeyTables () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:243
243 char name[XkbKeyNameLength + 1];
(gdb)
_glfwPlatformInit () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:721
721 XInitThreads();
(gdb)
723 _glfw.x11.display = XOpenDisplay(NULL);
(gdb)
724 if (!_glfw.x11.display)
(gdb)
741 _glfw.x11.screen = DefaultScreen(_glfw.x11.display);
(gdb)
742 _glfw.x11.root = RootWindow(_glfw.x11.display, _glfw.x11.screen);
(gdb)
741 _glfw.x11.screen = DefaultScreen(_glfw.x11.display);
(gdb)
742 _glfw.x11.root = RootWindow(_glfw.x11.display, _glfw.x11.screen);
(gdb)
741 _glfw.x11.screen = DefaultScreen(_glfw.x11.display);
(gdb)
742 _glfw.x11.root = RootWindow(_glfw.x11.display, _glfw.x11.screen);
(gdb)
743 _glfw.x11.context = XUniqueContext();
(gdb)
745 if (!initExtensions())
(gdb)
initExtensions () at /home/pwaller/.local/src/github.com/go-gl/glfw/v3.2/glfw/glfw/src/x11_init.c:474
474 if (XRRQueryExtension(_glfw.x11.display,
(gdb)
478 if (XRRQueryVersion(_glfw.x11.display,
(gdb)
483 if (_glfw.x11.randr.major > 1 || _glfw.x11.randr.minor >= 3)
(gdb)
484 _glfw.x11.randr.available = GLFW_TRUE;
(gdb)
496 _glfw.x11.root);
(gdb)
495 XRRScreenResources* sr = XRRGetScreenResources(_glfw.x11.display,
(gdb)
496 _glfw.x11.root);
(gdb)
495 XRRScreenResources* sr = XRRGetScreenResources(_glfw.x11.display,
(gdb)
498 if (!sr->ncrtc || !XRRGetCrtcGammaSize(_glfw.x11.display, sr->crtcs[0]))
(gdb)
==1344==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x6ff345 (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x6ff345)
#1 0x6ed1dd (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x6ed1dd)
#2 0x71b91f (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x71b91f)
#3 0x4f06cf (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x4f06cf)
SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/gl41core-cube+0x6ff345)
Exiting
[Thread 0x7ffff2e02700 (LWP 1347) exited]
[Thread 0x7ffff3907700 (LWP 1346) exited]
[Thread 0x7ffff440c700 (LWP 1345) exited]
[Thread 0x7ffff7fc0440 (LWP 1344) exited]
warning: Error removing breakpoint 0
warning: Error removing breakpoint 0
warning: Error removing breakpoint 0
warning: Error removing breakpoint 0
warning: Error removing breakpoint 0
So it looks like the problematic line is line 498 of x11_init.c.
if (!sr->ncrtc || !XRRGetCrtcGammaSize(_glfw.x11.display, sr->crtcs[0]))
from example.
pwaller
commented on July 21, 2024
Ah wait, msan != -fsanitize=address.
If I use -fsanitize=memory, then the c program fails too:
Uninitialized bytes in read_iovec at offset 0 inside [0x70400000ec60, 18)
==1969==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x429e88 (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/init/a.out+0x429e88)
#1 0x7f997d193f28 (/usr/lib/x86_64-linux-gnu/libxcb.so.1+0x9f28)
#2 0x7f997d19431c (/usr/lib/x86_64-linux-gnu/libxcb.so.1+0xa31c)
#3 0x7f997d193a57 (/usr/lib/x86_64-linux-gnu/libxcb.so.1+0x9a57)
#4 0x7f997d197610 (/usr/lib/x86_64-linux-gnu/libxcb.so.1+0xd610)
#5 0x7f997f241809 (/usr/lib/x86_64-linux-gnu/libX11.so.6+0x3c809)
#6 0x7f997f232391 (/usr/lib/x86_64-linux-gnu/libX11.so.6+0x2d391)
#7 0x4b4172 (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/init/a.out+0x4b4172)
#8 0x4936ba (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/init/a.out+0x4936ba)
#9 0x48928c (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/init/a.out+0x48928c)
#10 0x7f997d8e682f (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#11 0x41bd88 (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/init/a.out+0x41bd88)
SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/pwaller/.local/src/github.com/go-gl/examples/gl41core-cube/init/a.out+0x429e88)
It might not be the same failure. But until someone can demonstrate that this is the go library's fault, I think we must conclude it is not for now. If this is a problem for you, please follow it up upstream. Given that the C program which just calls glfwInit fails, it seems unlikely that there is a quick fix on our side.
Thanks for reporting, but I will close this for now unless anyone follows up with further evidence and an actionable bug report.
from example.
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