Fix memory leak in fread (#4710)

NEWS.md

@@ -2,10 +2,15 @@
 
 # data.table [v1.14.6](https://github.com/Rdatatable/data.table/milestone/27?closed=1)
 
+## BUG FIXES
+
+1. `fread()` could leak memory, [#3292](https://github.com/Rdatatable/data.table/issues/3292). Thanks to @patrickhowerter for reporting, and Jim Hester for the fix. The fix requires R 3.4.0 or later. Loading `data.table` in earlier versions now highlights this issue on startup, asks users to upgrade R, and warns that we intend to upgrade `data.table`'s dependency from 8 year old R 3.1.0 (April 2014) to 5 year old R 3.4.0 (April 2017).
+
 ## NOTES
 
 1. Test 1962.098 has been modified to pass latest changes to `POSIXt` in R-devel.
 
+
 # data.table [v1.14.4](https://github.com/Rdatatable/data.table/milestone/26?closed=1)  (17 Oct 2022)
 
 ## NOTES

R/onAttach.R

@@ -32,6 +32,10 @@
         else
           paste0("This is ", Sys.info()["sysname"], ". This warning should not normally occur on Windows or Linux where OpenMP is turned on by data.table's configure script by passing -fopenmp to the compiler. If you see this warning on Windows or Linux, please file a GitHub issue."),
         "\n**********")
+    if (.Call(CbeforeR340)) {
+      # not base::getRversion()<"3.4.0" in case the user upgrades R but does not reinstall data.table; a reasonable mistake since data.table would seem to be the latest version
+      packageStartupMessage("**********\nThis data.table installation was compiled for R < 3.4.0 (Apr 2017) where fread() is known to leak memory. Please upgrade R and reinstall data.table to fix the leak. Maintaining and testing code branches to support very old versions increases development time so please do upgrade R. We intend to bump data.table's dependency from 8 year old R 3.1.0 (Apr 2014) to 5 year old R 3.4.0 (Apr 2017).\n**********")
+    }
   }
 }
 

inst/tests/benchmark.Rraw

@@ -168,3 +168,11 @@ test(1742.5, substring(x,nchar(x)-10,nchar(x)), c("50,28,95,76","62,87,23,40"))
 
 # Add scaled-up non-ASCII forder test 1896
 
+# fread leak, #3292
+dummy = rep("1\t2\t3\t4\t5", 10000000)
+writeLines(dummy, "out.tsv")
+start = gc()["Vcells",2]
+for (i in 1:10) data.table::fread("out.tsv")
+end = gc()["Vcells",2]
+test(, end/start < 1.05)
+

src/data.table.h

@@ -7,6 +7,9 @@
 #  define USE_RINTERNALS  // #3301
 #  define DATAPTR_RO(x) ((const void *)DATAPTR(x))
 #endif
+#if !defined(R_VERSION) || R_VERSION < R_Version(3, 4, 0)
+#  define SET_GROWABLE_BIT(x)  // #3292
+#endif
 #include <Rinternals.h>
 #define SEXPPTR_RO(x) ((const SEXP *)DATAPTR_RO(x))  // to avoid overhead of looped STRING_ELT and VECTOR_ELT
 #include <stdint.h>    // for uint64_t rather than unsigned long long
@@ -314,6 +317,7 @@ SEXP nqRecreateIndices(SEXP, SEXP, SEXP, SEXP, SEXP);
 SEXP fsort(SEXP, SEXP);
 SEXP inrange(SEXP, SEXP, SEXP, SEXP);
 SEXP hasOpenMP(void);
+SEXP beforeR340(void);
 SEXP uniqueNlogical(SEXP, SEXP);
 SEXP dllVersion(void);
 SEXP initLastUpdated(SEXP);

src/freadR.c

@@ -526,9 +526,11 @@ void setFinalNrow(size_t nrow) {
   if (length(DT)) {
     if (nrow == dtnrows)
       return;
-    for (int i=0; i<LENGTH(DT); i++) {
-      SETLENGTH(VECTOR_ELT(DT,i), nrow);  // TODO: realloc
-      SET_TRUELENGTH(VECTOR_ELT(DT,i), nrow);
+    const int ncol=LENGTH(DT);
+    for (int i=0; i<ncol; i++) {
+      SETLENGTH(VECTOR_ELT(DT,i), nrow);
+      SET_TRUELENGTH(VECTOR_ELT(DT,i), dtnrows);
+      SET_GROWABLE_BIT(VECTOR_ELT(DT,i));  // #3292
     }
   }
   R_FlushConsole(); // # 2481. Just a convenient place; nothing per se to do with setFinalNrow()

src/init.c

@@ -111,6 +111,7 @@ R_CallMethodDef callMethods[] = {
 {"Cinrange", (DL_FUNC) &inrange, -1},
 {"Cbetween", (DL_FUNC) &between, -1},
 {"ChasOpenMP", (DL_FUNC) &hasOpenMP, -1},
+{"CbeforeR340", (DL_FUNC) &beforeR340, -1},
 {"CuniqueNlogical", (DL_FUNC) &uniqueNlogical, -1},
 {"CfrollfunR", (DL_FUNC) &frollfunR, -1},
 {"CdllVersion", (DL_FUNC) &dllVersion, -1},
@@ -314,6 +315,16 @@ SEXP hasOpenMP(void) {
 }
 // # nocov end
 
+SEXP beforeR340(void) {
+  // used in onAttach.R for message about fread memory leak fix needing R 3.4.0
+  // at C level to catch if user upgrades R but does not reinstall data.table
+  #if defined(R_VERSION) && R_VERSION<R_Version(3,4,0)
+  return ScalarLogical(true);
+  #else
+  return ScalarLogical(false);
+  #endif
+}
+
 extern int *_Last_updated;  // assign.c
 
 SEXP initLastUpdated(SEXP var) {