Build failure on Arch Linux due to -Werror=format-security

[awvwgk]

Trying to build the latest classic flang release (20211221) against LLVM 13 on Arch Linux leads to the following failure when compiling the classic flang driver:

[300/1624] Building CXX object tools/flang2/f...xe/CMakeFiles/flang2.dir/llassem_common.cpp.o
FAILED: tools/flang2/flang2exe/CMakeFiles/flang2.dir/llassem_common.cpp.o 
/usr/bin/clang++ -DGTEST_HAS_RTTI=0 -DIN_FLANG2 -DMMD -DNOVECTORIZE -DPGFLANG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/include -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/include -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/include -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/shared -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/include/flang -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/lib/scutil -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/flang2exe -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/x86_64 -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/utils/symtab -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/utils/ilitp -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/utils/ilmtp -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/utils/machar -I/home/awvwgk/software/aur/classic-flang/src/build-flang-x86_64/tools/flang2/utils/upper -I/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/shared/utils -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions         -Wp,-D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security         -fstack-clash-protection -fcf-protection -Wp,-D_GLIBCXX_ASSERTIONS -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -fdiagnostics-color -ffunction-sections -fdata-sections -std=c++11 -fno-common -Woverloaded-virtual -Wcast-qual -fno-strict-aliasing -pedantic -Wno-long-long -Wall -W -Wno-unused-parameter -Wwrite-strings -O3 -DNDEBUG  -fno-exceptions -fno-rtti -MD -MT tools/flang2/flang2exe/CMakeFiles/flang2.dir/llassem_common.cpp.o -MF tools/flang2/flang2exe/CMakeFiles/flang2.dir/llassem_common.cpp.o.d -o tools/flang2/flang2exe/CMakeFiles/flang2.dir/llassem_common.cpp.o -c /home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp
In file included from /home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:13:
In file included from /home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.h:14:
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/ll_structure.h:697:12: warning: flexible array members are a C99 feature [-Wc99-extensions]
  LL_MDRef elem[];
           ^
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:124:23: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
      fprintf(ASMFIL, str);
                      ^~~
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:124:23: note: treat the string as an argument to avoid this
      fprintf(ASMFIL, str);
                      ^
                      "%s", 
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:131:25: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
        fprintf(ASMFIL, s);
                        ^
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:131:25: note: treat the string as an argument to avoid this
        fprintf(ASMFIL, s);
                        ^
                        "%s", 
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:164:7: warning: variable 'area' set but not used [-Wunused-but-set-variable]
  int area;
      ^
/home/awvwgk/software/aur/classic-flang/src/flang-flang_20211221/tools/flang2/flang2exe/llassem_common.cpp:742:7: warning: variable 'n' set but not used [-Wunused-but-set-variable]
  int n, bytes;
      ^
3 warnings and 2 errors generated.
ninja: build stopped: subcommand failed

Building with makepkg at the moment, this is the build hook:

build() {
  cd "${srcdir}"
  PREFIX=/usr

  case "${CARCH}" in
    i?86|armv7)
      # lld needs all the address space it can get.
      LDFLAGS+=" -Wl,--large-address-aware"
      ;;
  esac

  local -a extra_args

  if check_option "debug" "y"; then
    extra_args+=(-DCMAKE_BUILD_TYPE=Debug)
  else
    extra_args+=(-DCMAKE_BUILD_TYPE=Release)
  fi

  if [ "${_compiler}" == "clang" ]; then
    export CC='clang'
    export CXX='clang++'
    extra_args+=(-DLLVM_ENABLE_LLD=ON)
  fi

  [[ -d build-flang-${CARCH} ]] && rm -rf build-flang-${CARCH}
  mkdir build-flang-${CARCH} && pushd build-flang-${CARCH}

  cmake \
    -GNinja \
    -Wno-dev \
    -DCMAKE_INSTALL_PREFIX=$PREFIX \
    -DLLVM_CONFIG=$PREFIX/bin/llvm-config \
    -DCMAKE_CXX_COMPILER=$PREFIX/bin/clang++ \
    -DCMAKE_C_COMPILER=$PREFIX/bin/clang \
    -DCMAKE_Fortran_COMPILER=$PREFIX/bin/flang \
    -DCMAKE_Fortran_COMPILER_ID=Flang \
    -DLLVM_TARGETS_TO_BUILD=X86 \
    -DFLANG_LLVM_EXTENSIONS=ON \
    -DWITH_WERROR=OFF \
    ../flang-flang_${pkgver}

  cmake --build .
}

Any advice?

[kiranchandramohan]

@bryanpkc has been trying to get the code to compile without warnings but we are still not there yet withformat-security.

Can you compile without Werror=format-security, or is that compulsory in Arch Linux?

[awvwgk]

I think this is injected by Arch Linux in all CMake builds done via makepkg, I could try to filter this flag out again by patching the CMake build files.

[kiranchandramohan]

In addition, you might have to rebase since I reverted a recent patch that was causing a build failure.