COMP: Fix spFactor.c K&R prototypes for C23 compilers (GCC 15+/16)

[gdevenyi]

Problem

GCC 15+ (Fedora 42/43/44, GCC 16 locally) defaults to C23, where an empty () function prototype means (void) instead of K&R unspecified-args. VXL's bundled netlib v3p/netlib/sparse/spFactor.c has four block-scope re-declarations of FindBiggestInColExclude / FindLargestInCol with empty (), then calls them with arguments. C23 rejects this:

error: too many arguments to function 'FindBiggestInColExclude'; expected 0, have 3
error: conflicting types for 'FindBiggestInColExclude'; have 'RealNumber(void)'

This breaks the ITK build on every C23-default toolchain. Reported downstream in BIC-MNI/minc-toolkit-v2#197, which works around it by forcing -std=gnu17 on ITK's C flags — a build-flag workaround rather than a source fix.

Fix

The file already carries correct file-scope static prototypes (lines 81-82). Replace the four stale empty-paren block-scope re-declarations with the full signatures so () no longer collapses to (void) under C23. C-only; pure prototype tightening with no codegen change under pre-C23 compilers, and no global -std override required.

Validation

With GCC 16.1.1:

• pre-edit: gcc -std=c23 -fsyntax-only reproduces the too many arguments / conflicting types errors above
• post-edit: compiles cleanly with no -std override

Note: gcc-16 detection in vcl/vcl_compiler.h is already present (VCL_GCC_16, cascade extended through gcc-20 in 4f97f72), so no compiler-detection change is needed.

🤖 Generated with Claude Code

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[greptile-apps]

Greptile Summary

Fixes a C23 build regression in VXL's bundled netlib spFactor.c by replacing four stale K&R empty-paren block-scope function re-declarations with explicit parameter-typed prototypes. The new signatures are identical to the existing file-scope static prototypes already present at lines 81-82, so no semantic or codegen change occurs under any compiler.

• Three block-scope RealNumber FindBiggestInColExclude() re-declarations are updated to FindBiggestInColExclude( MatrixPtr, ElementPtr, int ), matching the file-scope static prototype.
• One block-scope RealNumber FindLargestInCol() re-declaration is updated to FindLargestInCol( ElementPtr ), likewise matching its file-scope prototype.

Confidence Score: 5/5

Straightforward prototype-only fix with no logic or codegen change; the updated signatures exactly mirror the existing file-scope static declarations.

All four block-scope re-declarations are updated to signatures that already exist verbatim as file-scope static prototypes in the same file. There is no behavior change under pre-C23 compilers and the build error under C23 is correctly resolved.

No files require special attention.

Important Files Changed

Filename	Overview
Modules/ThirdParty/VNL/src/vxl/v3p/netlib/sparse/spFactor.c	Four stale K&R empty-paren block-scope re-declarations replaced with full parameter-typed prototypes matching the existing file-scope static declarations at lines 81-82; no logic change.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[C23 compiler GCC 15 or later] -->|empty parens means void| B[Block-scope re-declaration RealNumber FindBiggestInColExclude]
    B -->|conflicting types error| C[Build failure]
    D[File-scope static prototype with full parameter list] -->|already correct| E[Block-scope re-declaration updated to match]
    E -->|consistent types| F[Builds cleanly under C23]

Loading

_{Reviews (1): Last reviewed commit: "COMP: Give spFactor.c K&R prototypes ful..." | Re-trigger Greptile}

[dzenanz]

@hjmjohnson Is there some chance you could fix CI in release-4.14 branch?

[hjmjohnson]

@hjmjohnson Is there some chance you could fix CI in release-4.14 branch?

@dzenanz I can work with "claude" and monitor it's efforts :). Almost certainly a low human effort at this point!

[hjmjohnson]

The red checks here are infrastructure, not this PR: the release-4.14 Azure pipelines request hosted agent images retired years ago. CI restoration is underway in #6440; once that merges, a re-run/rebase here should go green.