[io] Prevent losing data due to SIGTERM (under Unix)

core/base/inc/TROOT.h

@@ -336,6 +336,7 @@ friend TROOT *ROOT::Internal::GetROOT2();
    Int_t             Timer() const { return fTimer; }
 
    //---- static functions
+   static void        CleanUpROOTAtExit();
    static Int_t       DecreaseDirLevel();
    static Int_t       GetDirLevel();
    static const char *GetMacroPath();
@@ -348,6 +349,7 @@ friend TROOT *ROOT::Internal::GetROOT2();
    static Int_t       ConvertVersionCode2Int(Int_t code);
    static Int_t       ConvertVersionInt2Code(Int_t v);
    static Int_t       RootVersionCode();
+   static void        WriteCloseAllFiles();
    static const std::vector<std::string> &AddExtraInterpreterArgs(const std::vector<std::string> &args);
    static const char**&GetExtraInterpreterArgs();
 

core/base/src/TROOT.cxx

@@ -226,10 +226,37 @@ static Int_t ITIMQQ(const char *time)
    return 100*hh + mm;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// Write and Close all open writable TFiles, useful to be called when SIGTERM is caught.
+
+void TROOT::WriteCloseAllFiles()
+{
+   if (gROOT) {
+      R__LOCKGUARD(gROOTMutex);
+
+      if (gROOT->GetListOfFiles()) {
+         TIter next(gROOT->GetListOfFiles());
+         while (TObject *obj = next()) {
+            if (obj && obj->InheritsFrom(TClass::GetClass("TFile", kFALSE, kTRUE))) {
+               TMethodCall callIsWritable(obj->IsA(), "IsWritable", "");
+               Longptr_t retLong = 0;
+               callIsWritable.Execute((void *)(obj), retLong);
+               if (retLong == 1) {
+                  TMethodCall callWrite(obj->IsA(), "Write", "");
+                  callWrite.Execute((void *)(obj));
+                  TMethodCall callClose(obj->IsA(), "Close", "");
+                  callClose.Execute((void *)(obj));
+               }
+            }
+         }
+      }
+   }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// Clean up at program termination before global objects go out of scope.
 
-static void CleanUpROOTAtExit()
+void TROOT::CleanUpROOTAtExit()
 {
    if (gROOT) {
       R__LOCKGUARD(gROOTMutex);

core/textinput/src/textinput/TerminalConfigUnix.cpp

@@ -24,6 +24,8 @@
 #include <stdio.h>
 #include <cstring>
 
+#include <TROOT.h>
+
 using namespace textinput;
 using std::memcpy;
 using std::signal;
@@ -104,6 +106,11 @@ TerminalConfigUnix::HandleSignal(int signum) {
     }
   }
 
+  // gentle save and close if SIGTERM
+  if (signum == SIGTERM) {
+     TROOT::WriteCloseAllFiles();
+     TROOT::CleanUpROOTAtExit();
+  }
   // No previous handler found, re-raise to get default handling:
   signal(signum, SIG_DFL); // unregister ourselves
   raise(signum); // terminate through default handler

io/io/test/CMakeLists.txt

@@ -5,7 +5,7 @@
 # For the list of contributors see $ROOTSYS/README/CREDITS.
 
 ROOT_ADD_GTEST(RRawFile RRawFile.cxx LIBRARIES RIO)
-ROOT_ADD_GTEST(TFile TFileTests.cxx LIBRARIES RIO)
+ROOT_ADD_GTEST(TFile TFileTests.cxx LIBRARIES RIO Hist)
 ROOT_ADD_GTEST(TBufferFile TBufferFileTests.cxx LIBRARIES RIO)
 ROOT_ADD_GTEST(TBufferMerger TBufferMerger.cxx LIBRARIES RIO Imt Tree)
 ROOT_ADD_GTEST(TBufferJSON TBufferJSONTests.cxx LIBRARIES RIO)

io/io/test/TFileTests.cxx

@@ -1,10 +1,12 @@
 #include <memory>
 #include <vector>
 #include <string>
+#include <csignal>
 
 #include "gtest/gtest.h"
 
 #include "TFile.h"
+#include "TH1I.h"
 #include "TMemFile.h"
 #include "TDirectory.h"
 #include "TKey.h"
@@ -201,3 +203,25 @@ TEST(TFile, MakeSubDirectory)
    EXPECT_EQ(std::string(gDirectory->GetPath()), "dirTest17824.root:/a/b/c");
    EXPECT_EQ(std::string(gDirectory->GetName()), "c");
 }
+
+// https://github.com/root-project/root/issues/13300
+TEST(TFile, Sigterm)
+{
+   auto filename = "out13300.root";
+   {
+      TFile file(filename, "RECREATE");
+      file.mkdir("subdir")->cd();
+      TH1I hist("h", "h", 10, 0., 1.);
+      hist.Fill(0.4);
+      // Since the real behavior is save+close+crash which would make the test fail,
+      // rather than calling directly std::raise(SIGTERM),
+      // we emulate the response to SIGTERM in TerminalConfigUnix before crash:
+      TROOT::WriteCloseAllFiles();
+      TROOT::CleanUpROOTAtExit();
+   }
+   {
+      TFile file(filename, "READ");
+      ASSERT_EQ(file.Get<TH1I>("subdir/h")->GetBinContent(5), 1);
+   }
+   gSystem->Unlink(filename);
+}