Build fails with GCC 16 default C23 (gnu23) due to old-style function declarations

[ahhyoushh]

Environment

• Commit: 064b5144f868c9359082cdeb39ac23a76a68728b
• OS: Fedora 44
• Compiler: GCC 16.1.1
• Architecture: x86_64

Description

A clean checkout fails to build with the default GCC 16 configuration on Fedora 44.

The build reports many errors of the form:

error: too many arguments to function 'HashKill'; expected 0, have 1
../utils/hash.h:107: note: declared here
extern void HashKill();

along with many similar errors such as:

error: number of arguments doesn't match prototype
error: conflicting types for ...
error: too many arguments to function ...

These occur across multiple modules (database, graphics, extract, commands, netmenu, etc.).

Steps to reproduce

git clone https://github.com/RTimothyEdwards/magic.git
cd magic

./configure
make -j$(nproc)

Result is the build fails with prototype mismatch errors.

Workaround

A simple workaround is

CFLAGS="-std=gnu17" ./configure
make -j$(nproc)

and it builds successfully.

From what I can tell, this appears to be related to GCC 15+ defaulting to gnu23, where empty parameter-list declarations (for example extern void Foo();) are interpreted differently than under previous defaults, exposing legacy K&R-style declarations throughout the codebase.

Question

Would you prefer a contribution that:

1. Adds a temporary build-system workaround (for example using -std=gnu17 where appropriate), or
2. Modernizes the old-style declarations/prototypes so the project builds cleanly under newer GCC defaults?

I'd be happy to work on this issue whichever direction you prefer. Thanks!

[ahhyoushh]

I noticed the PR #526 talking about exactly this.

I think we can add a temporary work around till yall modernize the old-style definition wherever appropriate.

[tskaar]

Duplicate: #470

See: #470 (comment) :

# This is for F42
CFLAGS="-std=c17 -D_DEFAULT_SOURCE=1 -g" ./configure
make

Fedora42/43 comes with gcc-16+ by default, which maybe -std=c23 by default and that is the main issue, this project source has a history rooted in c89 but expects c99/gnu99 as a minimum but should compile with c17 just fine.

Known issue, and will probably be fixed in "due time" :)