From: Nick Terrell <terrelln@fb.com>
Date: Wed, 2 Mar 2022 19:04:04 +0000 (-0800)
Subject: [programs] Fix infinite loop when empty input is passed to trainer
X-Git-Tag: v1.5.4^2~236^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=da737c7ab89f61f1ea7c392299137f6ffe6f9733;p=thirdparty%2Fzstd.git

[programs] Fix infinite loop when empty input is passed to trainer

When an empty input file was passed to the dictionary trainer, it would infinite loop.
The added test case exposes the bug, and is fixed with this PR.
---

diff --git a/programs/dibio.c b/programs/dibio.c
index fddbc9e57..f6757dd34 100644
--- a/programs/dibio.c
+++ b/programs/dibio.c
@@ -128,8 +128,11 @@ static int DiB_loadFiles(
     while ( nbSamplesLoaded < sstSize && fileIndex < nbFiles ) {
         size_t fileDataLoaded;
         S64 const fileSize = DiB_getFileSize(fileNamesTable[fileIndex]);
-        if (fileSize <= 0) /* skip if zero-size or file error */
+        if (fileSize <= 0) {
+            /* skip if zero-size or file error */
+            ++fileIndex;
             continue;
+        }
 
         f = fopen( fileNamesTable[fileIndex], "rb");
         if (f == NULL)
diff --git a/tests/cli-tests/dict-builder/empty-input.sh b/tests/cli-tests/dict-builder/empty-input.sh
new file mode 100755
index 000000000..b500bfebd
--- /dev/null
+++ b/tests/cli-tests/dict-builder/empty-input.sh
@@ -0,0 +1,9 @@
+#!/bin/sh
+set -e
+for i in $(seq 50); do
+    datagen -s$i > file$i
+done
+touch empty
+
+set -v
+zstd -q --train empty file*
diff --git a/tests/cli-tests/dict-builder/empty-input.sh.stderr.exact b/tests/cli-tests/dict-builder/empty-input.sh.stderr.exact
new file mode 100644
index 000000000..2747e766c
--- /dev/null
+++ b/tests/cli-tests/dict-builder/empty-input.sh.stderr.exact
@@ -0,0 +1 @@
+zstd -q --train empty file*