input.c was capable of generating a paragraph structure with no text

in it, if the input paragraph contained (say) an unrecognised
control command and nothing else. Such paragraphs can confuse back
ends later on, so input.c should refrain from generating them. Added
a check and a polite error message (just in case the user manages to
generate an empty paragraph using otherwise legal syntax).

[originally from svn r5629]

1 files changed, 13 insertions, 1 deletions

diff --git a/input.c b/input.c
index 493449c..d8d44f9 100644
--- a/input.c
+++ b/input.c
@@ -1529,7 +1529,19 @@ static void read_file(paragraph ***ret, input *in, indexdata *idx,
 	}
 	stk_free(parsestk);
 	prev_para_type = par.type;
-	addpara(par, ret);
+	/*
+	 * Before we add the paragraph to the output list, we
+	 * should check that there was any text in it at all; there
+	 * might not be if (for example) the paragraph contained
+	 * nothing but an unrecognised command sequence, and if we
+	 * put an empty paragraph on the list it may confuse the
+	 * back ends later on.
+	 */
+	if (par.words) {
+	    addpara(par, ret);
+	} else {
+	    error(err_emptypara, &par.fpos);
+	}
 	if (t.type == tok_eof)
 	    already = TRUE;
     }