diff --git a/source/src/BNFC/Backend/C.hs b/source/src/BNFC/Backend/C.hs
index 9f6f61bc..d4cecb24 100644
--- a/source/src/BNFC/Backend/C.hs
+++ b/source/src/BNFC/Backend/C.hs
@@ -62,7 +62,7 @@ makeC opts cf = do
 makefile :: String -> String -> String -> Doc
 makefile name prefix basename = vcat
     [ "CC = gcc -g"
-    , "CCFLAGS = --ansi -W -Wall -Wno-unused-parameter -Wno-unused-function -Wno-unneeded-internal-declaration ${CC_OPTS}"
+    , "CCFLAGS = --ansi -W -Wall -Wsign-conversion -Wno-unused-parameter -Wno-unused-function -Wno-unneeded-internal-declaration ${CC_OPTS}"
     -- The @#define _POSIX_C_SOURCE 200809L@ is now placed locally in
     -- the generated lexer.
     -- , "CCFLAGS = --ansi -W -Wall -Wno-unused-parameter -Wno-unused-function -Wno-unneeded-internal-declaration -D_POSIX_C_SOURCE=200809L ${CC_OPTS}"
diff --git a/source/src/BNFC/Backend/C/CFtoCPrinter.hs b/source/src/BNFC/Backend/C/CFtoCPrinter.hs
index 97236706..71054afd 100644
--- a/source/src/BNFC/Backend/C/CFtoCPrinter.hs
+++ b/source/src/BNFC/Backend/C/CFtoCPrinter.hs
@@ -155,6 +155,7 @@ mkCFile cf groups = concat
       "/*** Pretty Printer and Abstract Syntax Viewer ***/",
       "",
       "#include <ctype.h>   /* isspace */",
+      "#include <stddef.h>  /* size_t */",
       "#include <stdio.h>",
       "#include <string.h>",
       "#include <stdlib.h>",
@@ -164,8 +165,8 @@ mkCFile cf groups = concat
       "",
       "int _n_;",
       "char *buf_;",
-      "int cur_;",
-      "int buf_size;",
+      "size_t cur_;",
+      "size_t buf_size;",
       ""
      ]
     printBasics = unlines
@@ -266,8 +267,8 @@ mkCFile cf groups = concat
      [
       "void bufAppendS(const char *s)",
       "{",
-      "  int len = strlen(s);",
-      "  int n;",
+      "  size_t len = strlen(s);",
+      "  size_t n;",
       "  while (cur_ + len >= buf_size)",
       "  {",
       "    buf_size *= 2; /* Double the buffer size */",
@@ -314,7 +315,7 @@ mkCFile cf groups = concat
       "  buf_ = temp;",
       "}",
       "char *buf_;",
-      "int cur_, buf_size;",
+      "size_t cur_, buf_size;",
       ""
      ]
 
diff --git a/source/src/BNFC/Backend/CPP/Makefile.hs b/source/src/BNFC/Backend/CPP/Makefile.hs
index eb264add..0ecc16d5 100644
--- a/source/src/BNFC/Backend/CPP/Makefile.hs
+++ b/source/src/BNFC/Backend/CPP/Makefile.hs
@@ -8,7 +8,7 @@ import BNFC.PrettyPrint
 makefile :: String -> String -> String -> Doc
 makefile prefix name basename = vcat
     [ mkVar "CC" "g++ -g"
-    , mkVar "CCFLAGS" "--ansi -W -Wall -Wno-unused-parameter -Wno-unused-function -Wno-unneeded-internal-declaration"
+    , mkVar "CCFLAGS" "--ansi -W -Wall -Wsign-conversion -Wno-unused-parameter -Wno-unused-function -Wno-unneeded-internal-declaration"
     , ""
     , mkVar "FLEX" "flex"
     , mkVar "FLEX_OPTS" ("-P" ++ prefix)
diff --git a/source/src/BNFC/Backend/CPP/PrettyPrinter.hs b/source/src/BNFC/Backend/CPP/PrettyPrinter.hs
index df64af51..1f1b6251 100644
--- a/source/src/BNFC/Backend/CPP/PrettyPrinter.hs
+++ b/source/src/BNFC/Backend/CPP/PrettyPrinter.hs
@@ -69,6 +69,7 @@ mkHFile useStl inPackage cf groups = unlines
     "",
     "#include \"Absyn.H\"",
     "#include <stdio.h>",
+    "#include <stddef.h>",
     "#include <string.h>",
     "#include <stdlib.h>",
     "",
@@ -111,11 +112,11 @@ mkHFile useStl inPackage cf groups = unlines
    [
     " protected:",
     "  char *buf_;",
-    "  int cur_, buf_size;",
+    "  std::size_t cur_, buf_size;",
     "",
     "  void inline bufAppend(const char *s)",
     "  {",
-    "    int end = cur_ + strlen(s);",
+    "    std::size_t end = cur_ + strlen(s);",
     "    if (end >= buf_size) {",
     "      do buf_size *= 2; /* Double the buffer size */",
     "      while (end >= buf_size);",
@@ -139,29 +140,20 @@ mkHFile useStl inPackage cf groups = unlines
     if useStl then render (nest 2 bufAppendString) else "",
     "  void inline bufReset(void)",
     "  {",
-    "    if (buf_) free(buf_);",
+    "    if (buf_) delete[] buf_;",
     "    buf_size = " ++ nsDefine inPackage "BUFFER_INITIAL" ++ ";",
-    "    buf_ = (char *) malloc(buf_size);",
-    "    if (!buf_) {",
-    "      fprintf(stderr, \"Error: Out of memory while allocating buffer!\\n\");",
-    "      exit(1);",
-    "    }",
+    "    buf_ = new char[buf_size];",
     "    memset(buf_, 0, buf_size);",
     "    cur_ = 0;",
     "  }",
     "",
     "  void inline resizeBuffer(void)",
     "  {",
-    "    char *temp = (char *) malloc(buf_size);",
-    "    if (!temp)",
-    "    {",
-    "      fprintf(stderr, \"Error: Out of memory while attempting to grow buffer!\\n\");",
-    "      exit(1);",
-    "    }",
+    "    char *temp = new char[buf_size];",
     "    if (buf_)",
     "    {",
     "      strcpy(temp, buf_);",
-    "      free(buf_);",
+    "      delete[] buf_;",
     "    }",
     "    buf_ = temp;",
     "  }",