error reading variable on Windows Docker Containers

J.R. Heisey
Fri Nov 15 18:00:00 GMT 2019

Why are you quoting the variable name?

SVO 460 Room 167

-----Original Message-----
From: <> On Behalf Of Jonah Graham
Sent: Friday, November 15, 2019 9:20 AM
To: GDB Development <>
Subject: [External] error reading variable on Windows Docker Containers

Hello folks,

I have a strange error using GDB on a Windows Docker container and I don't know where to start in diagnosing the problem.

Simply, when trying to print characters or strings I get "error reading variable". For example:

(gdb) p 'Z'
$1 = 90 '<error reading variable>
instead of:
$1 = 90 'Z'

Full log below. This is running a Windows Docker container (FROM using msys2's distribution of mingw-w64-x86_64-gdb.

Full command and output:

gdb -ex "p 'Z'" -ex "p/x 'Z'" -ex "p \"abcd\"" -ex "quit"
GNU gdb (GDB) 8.3.1
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-w64-mingw32".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
Find the GDB manual and other documentation resources online at:

For help, type "help".
Type "apropos word" to search for commands related to "word".
$1 = 90 '<error reading variable>
$2 = 0x5a
$3 = <error reading variable>

What I expect, and what I get on the same version of Windows Pro (1809) with the identical GDB when running on the host OS is:

$1 = 90 'Z'
$2 = 0x5a
$3 = "abcd"

Any guidance greatly welcome.

PS for those of you who might wonder why, I am in the process of setting up regression tests on Windows for a VS Code Debug Adapter for GDB by the Eclipse CDT project: I am hoping to run these tests in a container to improve reproducibility. At the moment our tests pass, except the ones for variables.

Thank you,

Jonah Graham
Kichwa Coders

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