C: ternary middle arm rejects comma expression

• Type: bug (C frontend / expression parser) — Track C
• Status: done
• Owner: Track CA
• Found / Opened: 2026-06-27, M5 sqlite bring-up ([[feature-c-desktop-lua-sqlite-path]]), after getpid cleared.
• Closed: 2026-06-27

Symptom

sqlite advanced to a parse error in a macro-expanded getVarint32 expression:

((u32)(nPayload)<(u32)0x80)
  ? (*(&pCell[nHeader])=(unsigned char)(nPayload)), 1
  : sqlite3PutVarint(...)

The parser consumed only the assignment as the ternary middle arm and then expected :, failing when it saw the comma before 1.

Cause

C's conditional operator grammar makes the middle arm a full expression, so a top-level comma belongs to that arm. ParseCExpr used itself for the middle arm, but top-level comma parsing lives in ParseCCommaExpr.

Fix

Use ParseCCommaExpr for the ?: middle arm.

Regression

Added test/cternary_middle_comma_b102.c, wired into make test-core.