gcc fails to cross compile Qt

[Svein Seldal]

Building fails when cross compiling building embedded Qt (not for X11). After a little while the compilation stops with the message:

{standard input}: Assembler messages:
{standard input}:26712: Error: selected processor does not support Thumb mode `swp r3,r2,[r1]'

The error occurs on arm-linux-gnueabi-gcc version 4.5.1 and 4.5.1. The error does not, however, occur on the Code Sourcery G++ Lite compiler (version 2010q1-202 - gcc 4.4.1)

Host system is Maverick, amd64. The bug has been confimed on g++-4.4-arm-linux-gnueabi version 4.4.4-14ubuntu4 and on g++-4.5-arm-linux-gnueabi version 4.5.1-7ubuntu1cross1.38

Steps to reproduce the bug:

*) Please note the attached patch is for configuring Qt to use the Ubuntu armel-cross compiler instead of using the code sourcery compiler.

$ git clone git://gitorious.org/qt/qt.git -b 4.7-stable
    Topmost commit is currently: caca740ea1219227008c303b5f2fac24af5a62a0
$ cd qt
$ git apply ../ubuntu-gnueabi.diff
$ cd ..
$ mkdir qt-build
$ cd qt-build
$ ../qt/configure \
    -opensource \
    -confirm-license \
    -hostprefix `pwd`/qt-bin \
    -prefix /opt/qt \
    -fast \
    -embedded arm \
    -little-endian \
    -platform linux-g++ \
    -xplatform qws/linux-arm-gnueabi-g++ \
    -arch arm \
    -no-openssl \
    -no-cups \
    -no-largefile \
    -no-qt3support \
    -no-webkit \
    -no-libmng \
    -no-libjpeg \
    -no-libtiff \
    -no-gif \
    -no-script \
    -no-scripttools \
    -no-sql-sqlite \
    -no-accessibility \
    -no-multimedia \
    -no-nis \
    -qt-mouse-pc \
    -plugin-mouse-pc \
    -exceptions \
    -xmlpatterns \
    -nomake demos \
    -nomake examples \
    -nomake docs \
    -nomake translations \
    -D QT_NO_QWS_CURSOR \
    -D QT_QWS_CLIENTBLIT
$ make

...
arm-linux-gnueabi-g++ -c -include .pch/release-shared-emb-arm/QtCore -pipe -march=armv7-a -mtune=cortex-a8 -mfloat-abi=softfp -mfpu=neon -fvisibility=hidden -fvisibility-inlines-hidden -Wall -W -D_REENTRANT -fPIC -DQT_SHARED -DQT_NO_QWS_CURSOR -DQT_QWS_CLIENTBLIT -DQT_BUILD_CORE_LIB -DQT_NO_USING_NAMESPACE -DQT_NO_CAST_TO_ASCII -DQT_ASCII_CAST_WARNINGS -DQT_MOC_COMPAT -DQT_USE_FAST_OPERATOR_PLUS -DQT_USE_FAST_CONCATENATION -DELF_INTERPRETER=\"/lib64/ld-linux-x86-64.so.2\" -DHB_EXPORT=Q_CORE_EXPORT -DQT_NO_DEBUG -I/home/user/temp/gcc-bug/qt/mkspecs/qws/linux-arm-gnueabi-g++ -I/home/user/temp/gcc-bug/qt/src/corelib -I../../include -I../../include/QtCore -I.rcc/release-shared-emb-arm -Iglobal -I/home/user/temp/gcc-bug/qt/src/3rdparty/zlib -I/home/user/temp/gcc-bug/qt/src/3rdparty/harfbuzz/src -I/home/user/temp/gcc-bug/qt/src/3rdparty/md5 -I/home/user/temp/gcc-bug/qt/src/3rdparty/md4 -I.moc/release-shared-emb-arm -I. -o .obj/release-shared-emb-arm/qobject.o /home/user/temp/gcc-bug/qt/src/corelib/kernel/qobject.cpp
{standard input}: Assembler messages:
{standard input}:26712: Error: selected processor does not support Thumb mode `swp r3,r2,[r1]'
make[1]: *** [.obj/release-shared-emb-arm/qobject.o] Error 1
make[1]: Leaving directory `/home/user/temp/gcc-bug/qt-build/src/corelib'
make: *** [sub-corelib-make_default-ordered] Error 2

[Marcin Juszkiewicz (hrw)]

OK, discussed it with people.

Problem lies in Qt which does not have proper support for Thumb2 instruction set which is used by default. Please add "-marm" into CFLAGS/CXXFLAGS to force normal ARM instruction set - should work.

[Marcin Juszkiewicz (hrw)]

ping

[Svein Seldal (sveinse)]

This is a confirmed bug in Qt and not in gcc. Using -marm fixes the issue.