SD.h Compile/Combiner bug or feature?

I have working code on a 2560, using environment Sloeber 4.3.1
Doing a tidy up and note warnings… Is it a Compile/Combiner bug or a ‘feature’?
If I remove the Serial.begin, then on some random builds, the warning goes away? Odd?

'Starting combiner
...
C:\Users\wortinguk\slober\arduinoPlugin\packages\arduino\hardware\avr\1.8.2\cores\arduino\main.cpp: In function 'main':
C:\Users\wortinguk\slober\arduinoPlugin\libraries\SD\1.2.4\src\SD.cpp:462:14: warning: 'pathidx' may be used uninitialized in this function [-Wmaybe-uninitialized]
     filepath += pathidx;
              ^
C:\Users\wortinguk\slober\arduinoPlugin\libraries\SD\1.2.4\src\SD.cpp:456:9: note: 'pathidx' was declared here
     int pathidx;
         ^
'Finished building:
...

test .ino

#include "Arduino.h"
#include <SPI.h>
#include <SD.h>

File sdFile;

void setup (void)
{
        Serial.begin(9600);

	SD.begin(10);
	sdFile = SD.open("/A/A.txt");
}

void loop()
{
}

Many thanks in advance
Dave

it is a warning and it is not in your code. ignore it

Hmm... If we eradicate warnings, I think we generally end up with better code.
To me, a warning is a potential run time error, sometime in the future.

wortinguk:
Hmm... If we eradicate warnings, I think we generally end up with better code.
To me, a warning is a potential run time error, sometime in the future.