Stop using SET_TRUELENGTH(), SETLENGTH(), SET_GROWABLE_BIT() (#1593)

* Stop using SET_TRUELENGTH(), SETLENGTH(), SET_GROWABLE_BIT()

Removes this NOTE:

File 'readr/libs/readr.so':
    Found non-API calls to R: ‘SETLENGTH’, ‘SET_GROWABLE_BIT’,
      ‘SET_TRUELENGTH’

  Compiled code should not call non-API entry points in R.

  See ‘Writing portable packages’ in the ‘Writing R Extensions’ manual,
  and section ‘Moving into C API compliance’ for issues with the use of
  non-API entry points.

* Quick benchmark study

* Add NEWS bullet

* Remove benchmark study

Author: jennybc

.Rbuildignore

@@ -29,6 +29,7 @@
 ^pkgdown$
 ^rcon$
 ^inst/rcon$
+^inst/bench$
 ^azure-pipelines\.yml$
 ^LICENSE\.md$
 ^\.github/workflows/R-CMD-check\.yaml$

NEWS.md

@@ -8,6 +8,10 @@
 * Help files below `man/` have been re-generated, as part of the effort to
   support HTML reference manuals on CRAN.
 
+* readr no longer uses `SETLENGTH()`, `SET_TRUELENGTH()`, or
+  `SET_GROWABLE_BIT()`. This change improves C API compliance, with a small
+  performance cost affecting only the legacy first edition parser.
+
 # readr 2.1.5
 
 * No major user-facing changes. Patch release with housekeeping changes and

src/Collector.h

@@ -48,17 +48,7 @@ class Collector {
     if (column_ == R_NilValue)
       return;
 
-#if R_VERSION >= R_Version(3, 4, 0)
-    if (n > 0 && n < n_) {
-      SET_TRUELENGTH(column_, n_);
-      SETLENGTH(column_, n);
-      SET_GROWABLE_BIT(column_);
-    } else {
-      column_ = Rf_lengthgets(column_, n);
-    }
-#else
     column_ = Rf_lengthgets(column_, n);
-#endif
 
     n_ = n;
   }