[flang-commits] [flang] [flang] Avoid undefined behaviour when parsing format expressions (PR #147539)

Wed Jul 9 07:42:07 PDT 2025

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-sles-build-only` running on `rocm-worker-hw-04-sles` while building `flang` at step 5 "compile-openmp".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/26612

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (compile-openmp) failure: build (failure)
...
6.668 [98/34/858] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/file.cpp.o
6.709 [97/34/859] Linking CXX executable /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/lib/libomptarget-amdgpu.bc
clang++: warning: joined argument expects additional value: '-mcpu=' [-Wunused-command-line-argument]
6.719 [96/34/860] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/internal-unit.cpp.o
6.781 [95/34/861] Linking CXX static library /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/lib/amdgcn-amd-amdhsa/libompdevice.a
6.787 [94/34/862] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/derived.cpp.o
6.803 [93/34/863] Building CXX object offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/MiscGen.cpp.o
6.804 [92/34/864] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/inquiry.cpp.o
6.890 [91/34/865] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/assign.cpp.o
6.894 [90/34/866] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/format.cpp.o
FAILED: flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/format.cpp.o 
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/./bin/clang++ --target=x86_64-unknown-linux-gnu -D_DEBUG -D_GLIBCXX_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/include -I/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/../flang/include -Iflang-rt -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 -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -UNDEBUG -fno-lto -fno-exceptions -fno-rtti -funwind-tables -fno-asynchronous-unwind-tables -U_GLIBCXX_ASSERTIONS -U_LIBCPP_ENABLE_ASSERTIONS -std=gnu++17 -MD -MT flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/format.cpp.o -MF flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/format.cpp.o.d -o flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/format.cpp.o -c /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/lib/runtime/format.cpp
In file included from /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/lib/runtime/format.cpp:9:
In file included from /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/include/flang-rt/runtime/format-implementation.h:18:
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang/include/flang/Common/format.h:14:10: fatal error: 'llvm/Support/MathExtras.h' file not found
   14 | #include "llvm/Support/MathExtras.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
6.938 [90/33/867] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/io-error.cpp.o
6.943 [90/32/868] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang/lib/Decimal/binary-to-decimal.cpp.o
6.973 [90/31/869] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/edit-input.cpp.o
6.992 [90/30/870] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/external-unit.cpp.o
7.097 [90/29/871] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/non-tbp-dio.cpp.o
7.149 [90/28/872] Building CXX object compiler-rt/lib/memprof/CMakeFiles/RTMemprof_dynamic.x86_64.dir/memprof_interceptors.cpp.o
7.188 [90/27/873] Building CXX object offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/PrintGen.cpp.o
7.198 [90/26/874] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/memory.cpp.o
7.205 [90/25/875] Building CXX object offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/EntryPointGen.cpp.o
7.281 [90/24/876] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/misc-intrinsic.cpp.o
7.340 [90/23/877] Building CXX object compiler-rt/lib/msan/CMakeFiles/clang_rt.msan-x86_64.dir/msan_interceptors.cpp.o
7.426 [90/22/878] Building CXX object offload/tools/offload-tblgen/CMakeFiles/offload-tblgen.dir/APIGen.cpp.o
7.485 [90/21/879] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/ragged.cpp.o
7.517 [90/20/880] Building CXX object compiler-rt/lib/tsan/rtl/CMakeFiles/clang_rt.tsan-x86_64.dir/tsan_interceptors_posix.cpp.o
7.542 [90/19/881] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/pointer.cpp.o
7.709 [90/18/882] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/numeric.cpp.o
7.742 [90/17/883] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/pseudo-unit.cpp.o
7.818 [90/16/884] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/io-api-minimal.cpp.o
7.944 [90/15/885] Building CXX object compiler-rt/lib/tsan/rtl/CMakeFiles/clang_rt.tsan-dynamic-x86_64.dir/tsan_interceptors_posix.cpp.o
7.982 [90/14/886] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/namelist.cpp.o
8.247 [90/13/887] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/edit-output.cpp.o
In file included from /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/lib/runtime/edit-output.cpp:10:
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/include/flang-rt/runtime/emit-encoded.h:49:40: warning: implicit conversion from 'const UnsignedChar' (aka 'const char16_t') to 'char32_t' may change the meaning of the represented code unit [-Wcharacter-conversion]
   49 |       auto len{EncodeUTF8(buffer + at, *uData++)};
      |                ~~~~~~~~~~              ^~~~~~~~
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/lib/runtime/edit-output.cpp:865:18: note: in instantiation of function template specialization 'Fortran::runtime::io::EmitEncoded<Fortran::runtime::io::IoStatementState, char16_t, true>' requested here
  865 |       ok = ok && EmitEncoded(io, &ch, 1);
      |                  ^
In file included from /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/lib/runtime/edit-output.cpp:10:
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/flang-rt/include/flang-rt/runtime/emit-encoded.h:49:40: warning: implicit conversion from 'const UnsignedChar' (aka 'const char16_t') to 'char32_t' may change the meaning of the represented code unit [-Wcharacter-conversion]
   49 |       auto len{EncodeUTF8(buffer + at, *uData++)};

```

</details>

https://github.com/llvm/llvm-project/pull/147539