The warning is not a bogus error IMO. It's indeed true that variable length arrays are not part of the C++ standard. But both GCC and clang treat variable length arrays as C++ extensions. It's just that clang is choosing to warn about the use, while apparently GCC does not. There's probably a way to turn off the warnings in clang but I don't know if I'd bother.
Most of my (limnited) research on the subject discourages use of variable length arrays in C++ for several reasons. There are other constructs in C++ that are recommended in place of C-style variable length arrays. From what I'm also reading, variable length array declarations of local variables is still an optional component of the C standard starting with C11. - Paul > On Aug 15, 2025, at 4:12 PM, Blake McBride <blake1...@gmail.com> wrote: > > If variable-length arrays are not supported by standard C++, why use them? > I'm sure you don't strictly need them, and by using them GNU-APL becomes > non-portable. > > --blake > > > > > On Fri, Aug 15, 2025 at 12:06 PM Dr. Jürgen Sauermann via Bugs and > suggestions for GNU APL <bug-apl@gnu.org <mailto:bug-apl@gnu.org>> wrote: >> Hi Louis, >> >> thanks, hopefully fixed in SVN 1880. >> >> I believe I have caught most of the C++ warnings. The warning about >> dynamic arrays is somewhat bogus since every C++ compiler that I know of >> supports dynamic arrays event though they are not standardised in C++ (and >> only god knows why not). >> >> I haven't touched the ld warnings; it seems like these linker flags are >> needed on >> some platforms. It might be that re-running libtoolize and/or aclocal gets >> rid of >> these warnings. >> >> Best Regards, >> Jürgen >> >> >> On 8/12/25 20:18, Louis Chretien wrote: >>> Yes, it did. The build was successful despite the warnings. >>> >>> — >>> Louis Chrétien >>> lchret...@mac.com <mailto:lchret...@mac.com> >>> >>>> On Aug 12, 2025, at 13:18, Dr. Jürgen Sauermann <mail@jürgen-sauermann.de> >>>> <mailto:mail@j%C3%BCrgen-sauermann.de> wrote: >>>> >>>> Hi Louis, >>>> >>>> I will look into this. Did the build produce a working apl binary despite >>>> the warnings? >>>> >>>> Thanks, >>>> Jürgen >>>> >>>> >>>> On 7/21/25 18:33, Louis Chretien via Bugs and suggestions for GNU APL >>>> wrote: >>>>> There is a bunch of warnings on the latest build of GNU APL for Mac OS >>>>> 14.7.6: >>>>> >>>>> ============================== >>>>> >>>>> Backtrace.cc:1401:18: warning: variable length arrays in C++ are a Clang >>>>> extension [-Wvla-cxx-extension] >>>>> 1401 | char si[strlen(const_si) + 1]; >>>>> | ^~~~~~~~~~~~~~~~~~~~ >>>>> Backtrace.cc:1401:25: note: read of non-constexpr variable 'const_si' is >>>>> not allowed in a constant expression >>>>> 1401 | char si[strlen(const_si) + 1]; >>>>> | ^ >>>>> Backtrace.cc:1400:23: note: declared here >>>>> 1400 | const char * const_si = strings[size - i - 1]; >>>>> | ^ >>>>> 1 warning generated. >>>>> >>>>> Bif_F12_INDEX_OF.cc:75:22: warning: variable length arrays in C++ are a >>>>> Clang extension [-Wvla-cxx-extension] >>>>> 75 | ShapeItem zz[rk_Z]; >>>>> | ^~~~ >>>>> Bif_F12_INDEX_OF.cc:75:22: note: initializer of 'rk_Z' is not a constant >>>>> expression >>>>> Bif_F12_INDEX_OF.cc:70:13: note: declared here >>>>> 70 | const sRank rk_Z = Z->get_rank(); >>>>> | ^ >>>>> 1 warning generated. >>>>> >>>>> PrimitiveFunction.cc:538:20: warning: variable length arrays in C++ are a >>>>> Clang extension [-Wvla-cxx-extension] >>>>> 538 | ShapeItem weight_Z[rank_Z]; >>>>> | ^~~~~~ >>>>> PrimitiveFunction.cc:538:20: note: read of non-const variable 'rank_Z' is >>>>> not allowed in a constant expression >>>>> PrimitiveFunction.cc:517:11: note: declared here >>>>> 517 | ShapeItem rank_Z = 0; >>>>> | ^ >>>>> 1 warning generated. >>>>> >>>>> Quad_CR.cc:1143:16: warning: variable length arrays in C++ are a Clang >>>>> extension [-Wvla-cxx-extension] >>>>> 1143 | UTF8 bytes_utf[len_B + 10]; >>>>> | ^~~~~~~~~~ >>>>> Quad_CR.cc:1143:16: note: initializer of 'len_B' is not a constant >>>>> expression >>>>> Quad_CR.cc:1141:17: note: declared here >>>>> 1141 | const ShapeItem len_B = B->element_count(); >>>>> | ^ >>>>> Quad_CR.cc:1723:32: warning: variable 'bi' set but not used >>>>> [-Wunused-but-set-variable] >>>>> 1723 | if (const APL_Integer bi = cell_B.get_near_int()) >>>>> chunk |= bit; >>>>> | ^ >>>>> 2 warnings generated. >>>>> >>>>> Quad_DLX.cc:465:16: warning: variable length arrays in C++ are a Clang >>>>> extension [-Wvla-cxx-extension] >>>>> 465 | char rows_used[rows]; >>>>> | ^~~~ >>>>> Quad_DLX.cc:465:16: note: implicit use of 'this' pointer is only allowed >>>>> within the evaluation of a call to a 'constexpr' member function >>>>> Quad_DLX.cc:478:18: warning: variable length arrays in C++ are a Clang >>>>> extension [-Wvla-cxx-extension] >>>>> 478 | int row[cols]; >>>>> | ^~~~ >>>>> Quad_DLX.cc:478:18: note: implicit use of 'this' pointer is only allowed >>>>> within the evaluation of a call to a 'constexpr' member function >>>>> 2 warnings generated. >>>>> >>>>> Tokenizer.cc:966:13: warning: variable length arrays in C++ are a Clang >>>>> extension [-Wvla-cxx-extension] >>>>> 966 | char buffer[int_digits.size() + fract_digits.size() + >>>>> expo_digits.size() + 20]; >>>>> | >>>>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>>>> Tokenizer.cc:966:24: note: non-constexpr function 'size' cannot be used >>>>> in a constant expression >>>>> 966 | char buffer[int_digits.size() + fract_digits.size() + >>>>> expo_digits.size() + 20]; >>>>> | ^ >>>>> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/string:1284:65: >>>>> note: declared here >>>>> 1284 | _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 size_type >>>>> size() const _NOEXCEPT { >>>>> | ^ >>>>> 1 warning generated. >>>>> >>>>> UCS_string_vector.cc:228:25: warning: variable length arrays in C++ are a >>>>> Clang extension [-Wvla-cxx-extension] >>>>> 228 | ShapeItem column_widths[column_count]; >>>>> | ^~~~~~~~~~~~ >>>>> UCS_string_vector.cc:228:25: note: function parameter 'column_count' with >>>>> unknown value cannot be used in a constant expression >>>>> UCS_string_vector.cc:225:59: note: declared here >>>>> 225 | UCS_string_vector::print_table(std::ostream & out, size_t >>>>> column_count) const >>>>> | ^ >>>>> 1 warning generated. >>>>> >>>>> UserFunction.cc:638:13: warning: variable length arrays in C++ are a >>>>> Clang extension [-Wvla-cxx-extension] >>>>> 638 | char status[get_text_size()]; status[0] = Function_header; >>>>> | ^~~~~~~~~~~~~~~ >>>>> UserFunction.cc:638:13: note: implicit use of 'this' pointer is only >>>>> allowed within the evaluation of a call to a 'constexpr' member function >>>>> UserFunction.cc:731:13: warning: variable length arrays in C++ are a >>>>> Clang extension [-Wvla-cxx-extension] >>>>> 731 | char status[get_text_size()]; status[0] = Function_header; >>>>> | ^~~~~~~~~~~~~~~ >>>>> UserFunction.cc:731:13: note: implicit use of 'this' pointer is only >>>>> allowed within the evaluation of a call to a 'constexpr' member function >>>>> UserFunction.cc:856:35: warning: variable 'ec' set but not used >>>>> [-Wunused-but-set-variable] >>>>> 856 | if (const ErrorCode ec = >>>>> transform_new_multi_lines()) >>>>> | ^ >>>>> UserFunction.cc:875:35: warning: variable 'ec' set but not used >>>>> [-Wunused-but-set-variable] >>>>> 875 | if (const ErrorCode ec = >>>>> transform_old_multi_lines()) >>>>> | ^ >>>>> UserFunction.cc:1414:24: warning: variable 'ec' set but not used >>>>> [-Wunused-but-set-variable] >>>>> 1414 | if (const ErrorCode ec = parser.parse(body_text, body, true)) >>>>> | ^ >>>>> 5 warnings generated. >>>>> >>>>> ============================== >>>>> >>>>> Also, there is an option on the ld command that should probably be >>>>> removed in the makefile: >>>>> >>>>> ============================== >>>>> >>>>> checking for -single_module linker flag... ld: warning: -single_module is >>>>> obsolete >>>>> no >>>>> ld: warning: -bind_at_load is deprecated on macOS >>>>> >>>>> ============================== >>>>> >>>>> --- >>>>> Louis Chrétien >>>>> lchret...@mac.com <mailto:lchret...@mac.com> >>>> >>
