dean

Whilst Bit::Vector is available as a Debian package in libbit-vector-perl, when installing it using cpanm the compile failed for me.

The installation crashed during the make stage, throwing a specific compiler error regarding false and true tokens:

Building Bit-Vector-7.4
...
cc -c   -D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2 -O2   -DVERSION=\"7.4\" -DXS_VERSION=\"7.4\" -fPIC "-I/home/dean/perl5/perlbrew/perls/perl-5.40.3/lib/5.40.3/x86_64-linux-thread-multi/CORE"   BitVector.c
In file included from BitVector.c:12:
ToolBox.h:98:20: error: cannot use keyword 'false' as enumeration constant
   98 |              enum { false, true };
      |                    ^~~~~
ToolBox.h:98:20: note: 'false' is a keyword with '-std=c23' onwards
make: *** [Makefile:343: BitVector.o] Error 1
-> FAIL Installing Bit::Vector failed.

Why this happens:

The issue stems from modern Linux distributions upgrading their default compiler (like GCC 15+) to use the C23 (ISO C 2023) standard. In C23, false and true became official, reserved language keywords[cite: 2]. Because Bit::Vector is an older module, its internal ToolBox.h file explicitly tries to define them inside an enum block for legacy compatibility, which modern C23 compliance strictly forbids[cite: 2].

A solution that worked was:

cpanm --configure-args="OPTIMIZE='-O2 -std=gnu17'" Bit::Vector

What this does:

• --configure-args
  Passes arguments directly to the underlying Makefile.PL build script[cite: 2].
• OPTIMIZE='-O2 -std=gnu17'
  Overrides the default compiler optimization settings[cite: 2]. It keeps standard -O2 optimization performance but strictly forces the compiler to treat the codebase as GNU C17 instead of C23[cite: 2]. This bypasses the keyword restrictions and allows the legacy enum declaration to succeed flawlessly[cite: 2].

Hopefully this will help someone else running into the same roadblock!