Error: attempt to get value of unresolved symbol `L0'

[Pali Rohár]

Hello!

During development and debugging of U-Boot bootloader I got strange
error from ARM GNU assembler, which looks like a bug in binutils or gcc.

Below is simplified code which can trigger it:

  $ cat test.S
  kernoffs:
  .word KERNEL_OFFSET - (. - CONFIG_SYS_TEXT_BASE)

  $ arm-linux-gnueabi-gcc -DKERNEL_OFFSET=0x40000 -DCONFIG_SYS_TEXT_BASE=0x80008000 -pipe -c test.S
  {standard input}: Assembler messages:
  {standard input}: Error: attempt to get value of unresolved symbol `L0'

I do not use any L0 symbol in the code, so error message seems to be
incorrect. And also I do not think that there is issue in that simple
assembler code.

On the other hand, if I declare negated value then compilation passes
without any error/warning. Code is:

  kernoffs:
  .word . - CONFIG_SYS_TEXT_BASE - KERNEL_OFFSET

It is quite strange that negated value can be compiled by gcc/as without
issue here.

I was told that I should report this issue, so I'm sending email to
binutils and gcc mailing list.

Do you have any idea where is the issue? It is a bug in gcc / as or is
there some syntax / semantic error in that simple example?

Just for the record I'm using standard ARM cross compiler available on
Debian 10 Buster system. Here are version information:

  $ arm-linux-gnueabi-gcc -v
  Using built-in specs.
  COLLECT_GCC=arm-linux-gnueabi-gcc
  COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/arm-linux-gnueabi/8/lto-wrapper
  Target: arm-linux-gnueabi
  Configured with: ../src/configure -v --with-pkgversion='Debian 8.3.0-2' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++ --prefix=/usr --with-gcc-major-version-only --program-suffix=-8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib --enable-multiarch --disable-sjlj-exceptions --with-arch=armv5te --with-float=soft --disable-werror --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=arm-linux-gnueabi --program-prefix=arm-linux-gnueabi- --includedir=/usr/arm-linux-gnueabi/include
  Thread model: posix
  gcc version 8.3.0 (Debian 8.3.0-2)

  $ arm-linux-gnueabi-as --version
  GNU assembler (GNU Binutils for Debian) 2.31.1
  Copyright (C) 2018 Free Software Foundation, Inc.
  This program is free software; you may redistribute it under the terms of
  the GNU General Public License version 3 or later.
  This program has absolutely no warranty.
  This assembler was configured for a target of `arm-linux-gnueabi'.