Public bug reported:
Title: jtdx 2.2.159+improved-3build1 segfaults at startup: LTO build
leaves copy relocations of Qt symbols (QCoreApplication::self)
Package: jtdx 2.2.159+improved-3build1 (Ubuntu 26.04 "resolute", amd64)
Symptom
jtdx segfaults every time it starts, during QApplication construction
and before any window appears. It happens under both Wayland and
XWayland (QT_QPA_PLATFORM=xcb). Other Qt5 applications on the same
system run normally, including wsjtx.
Backtrace (xcb):
The faulting instruction is mov 0x8(%rdi),%r12 with rdi=0. The sender of
screenAdded, qGuiApp (that is, QCoreApplication::self), is null as seen
from libQt5Gui, even though QtCore has already set it. Under Wayland the
same crash shows up in QWaylandDisplay::initialize.
Cause
readelf -rW /usr/bin/jtdx | grep R_X86_64_COPY shows copy relocations
for about 35 Qt data symbols, including _ZN16QCoreApplication4selfE,
QArrayData::shared_null and many staticMetaObjects. wsjtx on the same
system has no Qt copy relocations.
The jtdx compile flags do include -fPIC; Qt5's CMake usage requirements
add it to the Qt-using targets. But the package is built with LTO
(-flto=auto), so the code is generated at link time, as PIE (the
toolchain default). That brings back direct, PC-relative access to Qt's
global data, which the linker satisfies with copy relocations. The
executable then has its own copy of QCoreApplication::self, separate
from the one QtCore sets, so libQt5Gui sees null and segfaults.
Linking with -Wl,-z,nocopyreloc confirms this. The copy relocations
become text relocations, and at load time ld.so reports hundreds of
Symbol '...' causes overflow in R_X86_64_PC32 relocation for the same Qt
symbols.
Fix (tested)
Turning off LTO in debian/rules produces a working binary, with no Qt copy
relocations and no TEXTREL:
---- debian/rules ----
#!/usr/bin/make -f
export DEB_BUILD_MAINT_OPTIONS = optimize=-lto
ifeq ($(DEB_TARGET_ARCH),armel)
export DEB_BUILD_MAINT_OPTIONS += hardening=-stackclash
endif
%:
dh $@
override_dh_auto_configure:
# put documentation in /usr/share/doc/jtdx instead of .../JTDX
# don't install HTML documentation, it's the unmodified wsjtx document
(in 2.2.159)
dh_auto_configure -- \
-DCMAKE_INSTALL_DOCDIR=share/doc/jtdx \
-DWSJT_GENERATE_DOCS=NO
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: jtdx 2.2.159+improved-3build1
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sun Oct 4 16:56:56 2026
InstallationDate: Installed on 2022-12-16 (1388 days ago)
InstallationMedia: Ubuntu 22.04.1 LTS "Jammy Jellyfish" - Release amd64
(20220809.1)
SourcePackage: jtdx
UpgradeStatus: Upgraded to resolute on 2026-10-04 (1 days ago)
** Affects: jtdx (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
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https://bugs.launchpad.net/bugs/2169502
Title:
jtdx segfaults at startup due to LTO build
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