C: function returning function pointer prototype not registered

• Type: bug (C frontend / declaration parser) — Track C
• Status: done
• Owner: Track CA
• Found / Opened: 2026-06-27, M5 sqlite bring-up ([[feature-c-desktop-lua-sqlite-path]]), after the offsetof const-array bound wall was fixed.
• Closed: 2026-06-27

Symptom

sqlite stopped at:

pascal26:105031: error: call to undeclared function: sqlite3OsDlSym ()

Call site:

xInit = (sqlite3_loadext_entry)sqlite3OsDlSym(pVfs, handle, zEntry);

But the preprocessed source contained both a prototype and a definition:

static void (*sqlite3OsDlSym(sqlite3_vfs *, void *, const char *))(void);

static void (*sqlite3OsDlSym(sqlite3_vfs *pVfs, void *pHdle, const char *zSym))(void){
  return pVfs->xDlSym(pVfs, pHdle, zSym);
}

Cause

The declaration parser treated ret (*name(params))(retargs) like a function-pointer variable declarator, not like a real function named name. ParseCDeclType consumed the whole declarator, leaving no identifier for ParseCSubroutine to register, and CTopLevelIsFunc did not recognize the shape as a function.

Fix

ParseCDeclType now distinguishes:

• ret (*var)(args) — function-pointer variable/field/param/typedef.
• ret (*fn(params))(args) — function returning a function pointer.

For the second shape it captures the real function's name and parameter metadata. ParseCSubroutine consumes that side-channel and registers/compiles the routine as a normal C function returning Pointer.

Regression

Added test/cfn_return_fnptr_b105.c, wired into make test-core.

Result

sqlite advances to:

pascal26:33764: error: @ on external routine not supported; wrap it in a local routine ()

Filed [[bug-c-external-function-address-dlsym-sqlite]].