From 4ba4ea560280f54b476dd80f443dc6873ba96b86 Mon Sep 17 00:00:00 2001
From: Automatic Release Builder <build@flightgear.org>
Date: Thu, 4 Feb 2021 10:06:23 +0000
Subject: [PATCH] Adding code to see if it improves crash on computeHash.

Also add a test case to verify behaviour on empty files is correct.

Sentry-Id: FLIGHTGEAR-AY2
---
 simgear/io/sg_file.cxx         |  4 +++-
 simgear/io/test_repository.cxx | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/simgear/io/sg_file.cxx b/simgear/io/sg_file.cxx
index 9f223e34..1747e971 100644
--- a/simgear/io/sg_file.cxx
+++ b/simgear/io/sg_file.cxx
@@ -82,7 +82,9 @@ std::string SGFile::computeHash()
         [](char* p) { free(p); }};
 
     if (!buf) {
-        SG_LOG(SG_IO, SG_ALERT, "Failed to malloc buffer for SHA1 check");
+        // @TODO report out of memory error
+        SG_LOG(SG_IO, SG_ALERT, "Failed to malloc buffer for SHA1 check:" << file_name);
+        return {};
     }
 
     size_t readLen;
diff --git a/simgear/io/test_repository.cxx b/simgear/io/test_repository.cxx
index 6e3f86d4..ad4e9568 100644
--- a/simgear/io/test_repository.cxx
+++ b/simgear/io/test_repository.cxx
@@ -901,6 +901,27 @@ void testPersistentSocketFailure(HTTP::Client *cl) {
   verifyRequestCount("dirD/subdirDB/fileDBA", 1);
 }
 
+void testHashOnEmptyFile()
+{
+    std::unique_ptr<HTTPRepository> repo;
+    SGPath p(simgear::Dir::current().path());
+    p.append("sgfile_compute_hash");
+    simgear::Dir pd(p);
+    if (pd.exists()) {
+        pd.removeChildren();
+    } else {
+        pd.create(0700);
+    }
+
+    SGPath fPath = p / "test_empty_file";
+    
+    SGFile file(fPath);
+    file.open(SG_IO_OUT);
+    file.close();
+
+    const auto hash = file.computeHash();
+}
+
 int main(int argc, char* argv[])
 {
   sglog().setLogLevels( SG_ALL, SG_INFO );
@@ -951,6 +972,8 @@ int main(int argc, char* argv[])
     testRetryAfterSocketFailure(&cl);
     testPersistentSocketFailure(&cl);
 
+    testHashOnEmptyFile();
+
     std::cout << "all tests passed ok" << std::endl;
     return 0;
 }