Suppressing printf output from TMatrixBase (HEP-FCC#379)

* Suppressing printf output from TMatrixBase

* One more return

analyzers/dataframe/src/VertexFitterSimple.cc

@@ -6,12 +6,33 @@
 #include "TFile.h"
 #include "TString.h"
 
+#include <fcntl.h>
+
 //#include "TrkUtil.h"    // from delphes
 
 namespace FCCAnalyses {
 
 namespace VertexFitterSimple {
 
+int supress_stdout() {
+  fflush(stdout);
+
+  int ret = dup(1);
+  int nullfd = open("/dev/null", O_WRONLY);
+  // check nullfd for error omitted
+  dup2(nullfd, 1);
+  close(nullfd);
+
+  return ret;
+}
+
+void resume_stdout(int fd) {
+  fflush(stdout);
+  dup2(fd, 1);
+  close(fd);
+  std::cout << std::flush;
+}
+
 // -----------------------------------------------------------------------------
 
 VertexingUtils::FCCAnalysesVertex VertexFitter(
@@ -77,6 +98,11 @@ VertexFitter_Tk(int Primary, ROOT::VecOps::RVec<edm4hep::TrackState> tracks,
                 const ROOT::VecOps::RVec<edm4hep::TrackState> &alltracks,
                 bool BeamSpotConstraint, double bsc_sigmax, double bsc_sigmay,
                 double bsc_sigmaz, double bsc_x, double bsc_y, double bsc_z) {
+  // Suppressing printf() output from TMatrixBase:
+  // https://github.com/root-project/root/blob/722eb4652bfc79149df00c8b0e92d0837caf054c/math/matrix/src/TMatrixTBase.cxx#L662
+  // The solution found here:
+  // https://stackoverflow.com/questions/46728680/how-to-temporarily-suppress-output-from-printf
+  int fd = supress_stdout();
 
   // Units for the beam-spot : mum
   // See
@@ -117,8 +143,10 @@ VertexFitter_Tk(int Primary, ROOT::VecOps::RVec<edm4hep::TrackState> tracks,
 
   int Ntr = tracks.size();
   TheVertex.ntracks = Ntr;
-  if (Ntr <= 1)
+  if (Ntr <= 1) {
+    resume_stdout(fd);
     return TheVertex; // can not reconstruct a vertex with only one track...
+  }
 
   TVectorD **trkPar = new TVectorD *[Ntr];
   TMatrixDSym **trkCov = new TMatrixDSym *[Ntr];
@@ -214,6 +242,8 @@ VertexFitter_Tk(int Primary, ROOT::VecOps::RVec<edm4hep::TrackState> tracks,
   delete[] trkPar;
   delete[] trkCov;
 
+  resume_stdout(fd);
+
   return TheVertex;
 }