[logfile] the index rebuild didn't check the mtime if the file size was the same

Fixes #668

.gitignore

@@ -10,6 +10,8 @@
 *.pyc
 *.tmp
 *.trs
+*~
+.idea/
 Makefile
 Makefile.in
 TESTS_ENVIRONMENT
@@ -34,6 +36,7 @@ release/osx-pkg/
 release/outbox/
 release/vagrant-static-linux/.vagrant
 release/vagrant-static-linux/lnav
+cmake-build-debug/
 src/bin2c
 src/config.h
 src/config.h.in

src/logfile.cc

@@ -280,8 +280,10 @@ logfile::rebuild_result_t logfile::rebuild_index()
     }
 
     // Check the previous stat against the last to see if things are wonky.
-    if (this->lf_stat.st_size > st.st_size) {
-        log_info("truncated file detected, closing -- %s",
+    if (st.st_size < this->lf_stat.st_size ||
+        (this->lf_stat.st_size == st.st_size &&
+         this->lf_stat.st_mtime != st.st_mtime)) {
+        log_info("overwritten file detected, closing -- %s",
                  this->lf_filename.c_str());
         this->close();
         return RR_NO_NEW_LINES;

src/logfile.hh

@@ -64,7 +64,7 @@ class logline_observer;
  */
 class logfile_observer {
 public:
-    virtual ~logfile_observer() { };
+    virtual ~logfile_observer() = default;
 
     /**
      * @param lf The logfile object that is doing the indexing.
@@ -421,7 +421,7 @@ protected:
 
 class logline_observer {
 public:
-    virtual ~logline_observer() { };
+    virtual ~logline_observer() = default;
 
     virtual void logline_restart(const logfile &lf, size_t rollback_size) = 0;
 

test/Makefile.am

@@ -345,6 +345,7 @@ DISTCLEANFILES = \
 	*.bz2 \
 	hw.txt \
 	hw2.txt \
+	reload_test.0 \
 	truncfile.0 \
 	logfile_append.0 \
 	logfile_changed.0 \

test/lnav_doctests.cc

@@ -29,6 +29,8 @@
 
 #include "config.h"
 
+#include <fstream>
+
 #define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
 #include "doctest.hh"
 
@@ -36,9 +38,35 @@
 #include "view_curses.hh"
 #include "relative_time.hh"
 #include "unique_path.hh"
+#include "logfile.hh"
 
 using namespace std;
 
+std::vector<log_format *>& log_format::get_root_formats()
+{
+    static std::vector<log_format *> retval;
+
+    return retval;
+}
+
+TEST_CASE("overwritten-logfile") {
+    string fname = "reload_test.0";
+
+    ofstream(fname) << "test 1\n";
+
+    logfile_open_options loo;
+    logfile lf(fname, loo);
+    auto build_result = lf.rebuild_index();
+    CHECK(build_result == logfile::RR_NEW_LINES);
+    CHECK(lf.size() == 1);
+
+    sleep(1);
+    ofstream(fname) << "test 2\n";
+    auto rebuild_result = lf.rebuild_index();
+    CHECK(rebuild_result == logfile::RR_NO_NEW_LINES);
+    CHECK(lf.is_closed());
+}
+
 TEST_CASE("duration2str") {
     string val;