Maybe-uninitialized variables in Alignment/OfflineValidation/macros/momentumBiasValidation.C

[iarspider]

In CMSSW_14_0_CPP20_X_2024-01-22-1100 IB, the following warnings about potentially uninitialized variables are emitted:

  <...>: warning: 'lowLim' may be used uninitialized [-Wmaybe-uninitialized]
    97 |     { return ::new((void*)__location) _Tp(std::forward<_Args>(__args)...); }
      |              ^
<...>/Alignment/OfflineValidation/macros/momentumBiasValidation.C: In function 'extractgausparams':
<...>/Alignment/OfflineValidation/macros/momentumBiasValidation.C:43:12: note: 'lowLim' was declared here
   43 |     double lowLim;
      |            ^

  <...>: warning: 'upLim' may be used uninitialized [-Wmaybe-uninitialized]
    97 |     { return ::new((void*)__location) _Tp(std::forward<_Args>(__args)...); }
      |              ^
<...>/Alignment/OfflineValidation/macros/momentumBiasValidation.C: In function 'extractgausparams':
<...>/Alignment/OfflineValidation/macros/momentumBiasValidation.C:44:12: note: 'upLim' was declared here
   44 |     double upLim;
      |            ^

[iarspider]

assign Alignment/OfflineValidation

[cmsbuild]

New categories assigned: alca

@saumyaphor4252,@perrotta,@consuegs you have been requested to review this Pull request/Issue and eventually sign? Thanks

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[cmsbuild]

A new Issue was created by @iarspider .

@Dr15Jones, @sextonkennedy, @smuzaffar, @rappoccio, @makortel, @antoniovilela can you please review it and eventually sign/assign? Thanks.

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[perrotta]

@iarspider lowLim and upLim will never be uninitialized, because the loop that defines them (starting in https://github.com/cms-sw/cmssw/blob/master/Alignment/OfflineValidation/macros/momentumBiasValidation.C#L50) would at least be run once (when iteration = 0).

Of course, if we want to shut up the warning a whatever initial value can be given to those two variables, but nothing will change in the flow of the macro.

[mmusich]

@perrotta already correctly analyzed the situation at #43775 (comment).
I'd propose something like

diff --git a/Alignment/OfflineValidation/macros/momentumBiasValidation.C b/Alignment/OfflineValidation/macros/momentumBiasValidation.C
index 06b3069a5a7..b48833be321 100644
--- a/Alignment/OfflineValidation/macros/momentumBiasValidation.C
+++ b/Alignment/OfflineValidation/macros/momentumBiasValidation.C
@@ -40,8 +40,8 @@ namespace eop {
     double mean = f1->GetParameter(1);
     double deviation = f1->GetParameter(2);
 
-    double lowLim;
-    double upLim;
+    double lowLim{mean - (2.0 * deviation)};
+    double upLim{mean + (2.0 * deviation)};
     double newmean;
 
     double degrade = 0.05;

just to silence the warnings ;)