[willend]

Free-form text area

TL;DR: A %included library (or other C code file) whose last line has no trailing newline lost that line in the generated C. McStas echoed it to stdout instead, typically dropping a closing #endif or } and breaking compilation. This adds one lexer rule so the line is kept.

Found with the ESS BIFROST model (niess / mccode-antlr), where rfc-lib.h and rfc-lib.c end without a newline:

INFO: Regenerating c-file: bifrost.c
#endif // RFC_LIB_H}
...
./bifrost.c:14238:62: error: function definition is not allowed here

Change: one new <ccode> rule in mccode/src/instrument.l. It can only be the longest match on an unterminated last line; it pushes the line back with a newline appended, so the existing rules (%}, %include, plain code line) handle it. Details in docs/GRAMMAR/ADR-records/ADR_20261111_UNTERMINATED_LAST_LINE.md.

Test output (code generation only, patched vs. unpatched mcstas built from this branch / main):

• Unmodified BIFROST model: the brace/#endif errors are gone. (Its remaining errors are unrelated and handled upstream.)
• Generated C compared for the 369 McStas example instruments: 365 identical; 2 fail to generate both before and after (ESS_butterfly_MCPL_test, Test_Dispersion_relation_TAS, not investigated).
• 2 differ by one restored line (Supermirror_thin_substrate, Test_lib_supermirror_lib): mcstas-comps/share/supermirror-lib.h also lacks a final newline, and its closing comment was silently dropped until now. Comment only, no behaviour change.
• Two synthetic headers ending in an unterminated %include "read_table-lib" generate and pass a compiler syntax check.

Not tested: McXtrace (same lexer file, not built), Linux, Windows, and no compile-and-run of the example instruments.

Related upstream fix that adds the newlines: mcdotstar/mcstas-radial-filter-collimator#11

---

Declaration of use of AI-tools

• Please add a checkmark here if you used AI-tools during the work for this contribution
• Furter, please describe how / where and for what the tools were used: Claude Code was used to diagnose the failure, write the lexer rule and the ADR, and run the before/after comparison.

---

Development OS / boundary conditions

macOS arm64 (clang), flex/bison from conda-forge. No new dependencies.

---

PR Checklist for contributing to McStas/McXtrace

• My work touches the code-generator in mccode/src

  • I have added reasoning and documentation for the change through an ADR record in our GRAMMAR section
  • I am attaching test output in the comments

---

🤖 Generated with Claude Code

[willend]

mccode-antlr parity: no collateral effect expected. mccode-antlr (0.36.0) already keeps a last line that lacks a newline, so this PR brings the C code generator in line with it.

Test: %include "nonl-lib" in DECLARE, where nonl-lib.h ends in #endif // NONL_H_END and nonl-lib.c in } // NONL_C_END, both without a final newline.

code generator	both last lines in generated C
mcstas from main	no (echoed to stdout as #endif // NONL_H_END} // NONL_C_END)
mcstas from this PR	yes
mcstas-antlr 0.36.0	yes

Tested on macOS arm64 only.

🤖 Generated with Claude Code