Summary

• Replace unsafe #define dprintf if(DEBUG) printf macro with #define DPRINTF(...) do { if (DEBUG) printf(__VA_ARGS__); } while (0) across all 17 source files
• Add missing braces around single-statement if/else bodies in drill.c (SEI CERT EXP19-C)
• Remove all goto patterns in drill.c, replacing with structured control flow

Problem

The dprintf macro defined in 16 files as #define dprintf if(DEBUG) printf has two issues:

1. Dangling-else bug — the unbraced if causes else to bind incorrectly:

   if (error)
       dprintf("bad");    // expands to: if(0) printf("bad");
   else
       handle_ok();       // else binds to if(0), runs unconditionally

2. Shadows POSIX dprintf(3) — dprintf is a standard function for writing to file descriptors

main.c had an even more dangerous variant with two unbraced statements:

#define dprintf printf("%s():  ", __FUNCTION__); printf

Changes

Commit 1 — drill.c:

• Replace macro definition with safe DPRINTF(...) variadic macro
• Rename all call sites from dprintf() to DPRINTF()
• Add braces to single-statement if/else bodies
• Remove 3 goto patterns, replacing with structured control flow (parsing_done flag, for(;;) loop, found_junk flag)
• Add [[fallthrough]] annotation for pre-existing intentional fallthrough

Commit 2 — remaining 15 files + main.c:

• Same macro replacement across: gerber.c, gerbv.c, gerb_file.c, gerb_stats.c, project.c, interface.c, callbacks.c, render.c, attribute.c, draw.c, draw-gdk.c, export-drill.c, export-isel-drill.c, export-rs274x.c, drill_stats.c, main.c

Acknowledgment

The unsafe macro problem was originally identified by @henrygab in PR #226 (and earlier PR #210), which proposed fixes for drill.c. Those PRs were closed without merging. This PR applies the same category of fix using C99 variadic macros (appropriate for the project's C23 standard) and extends it to the full codebase.

Addresses

• drill.c -- unsafe macros are bad #220 — POSIX dprintf shadow / dangling-else hazard
• drill.c -- Avoid floating control statements #216 — Missing braces (SEI CERT EXP19-C) in drill.c

Test plan

• Clean build with zero new warnings (cmake .. && make -j$(nproc))
• Test suite: 94/104 pass (same baseline as develop)
• grep -r '#define dprintf' src/ returns zero results