Fix silent errors when reading lines from input files.

Handle files that don't end with a new line. Throw an error when the buffer
size is exceeded.

Fixes #516
Contributes to #1149

1 files changed, 12 insertions, 2 deletions

diff --git a/src/textual.cc b/src/textual.cc
index b8523dbe..3b6ef5f4 100644
--- a/src/textual.cc
+++ b/src/textual.cc
@@ -311,9 +311,14 @@ std::streamsize instance_t::read_line(char *& line)
 
   check_for_signal();
 
-  in.getline(context.linebuf, parse_context_t::MAX_LINE);
+  const size_t maxLine = parse_context_t::MAX_LINE;
+  in.getline(context.linebuf, maxLine);
   std::streamsize len = in.gcount();
 
+  if (in.fail() && len == (parse_context_t::MAX_LINE - 1)) {
+      throw_(parse_error, _f("Line exceeds %1% characters") % maxLine);
+  }
+
   if (len > 0) {
     context.linenum++;
 
@@ -329,7 +334,12 @@ std::streamsize instance_t::read_line(char *& line)
       line = context.linebuf;
     }
 
-    --len;
+    if (!in.eof()) {
+        // if we are not at the end of the file, len includes the new line character,
+        // even through it does not appear in linebuf
+        --len;
+    }
+
     while (len > 0 && std::isspace(line[len - 1])) // strip trailing whitespace
       line[--len] = '\0';