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GCC complains about possibly uninitialized variables when compiling with CXXFLAGS='-Og -g' #8280

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techgeeknz opened this issue Jul 22, 2020 · 0 comments · Fixed by #8281
Closed

GCC complains about possibly uninitialized variables when compiling with CXXFLAGS='-Og -g' #8280

techgeeknz opened this issue Jul 22, 2020 · 0 comments · Fixed by #8281

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@techgeeknz
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Version of OpenTTD

Since f44a9a5, I expect.

Expected result

The project compiles without issues, as it does with -O2 or -O3.

Actual result

Compiler logs this warning:

In file included from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/station_map.h:13:0,
                 from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:12:
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/rail_map.h: In function ‘void UpdateSignalsAroundSegment(SigFlags)’:
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/rail_map.h:452:68: warning: ‘trackdir’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   SetSignalStates(tile, GetSignalStates(tile) | SignalAlongTrackdir(trackdir));
                                                 ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:411:11: note: ‘trackdir’ was declared here
  Trackdir trackdir;
           ^~~~~~~~
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp: In function ‘SigFlags ExploreSegment(Owner)’:
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:343:26: warning: ‘enterdir’ may be used uninitialized in this function [-Wmaybe-uninitialized]
      if (dir != enterdir && (tracks & _enterdir_to_trackbits[dir])) { // any track incidating?
          ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:121:4: warning: ‘tile’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    if (this->data[i].tile == tile && this->data[i].dir == dir) {
    ^~
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:271:12: note: ‘tile’ was declared here
  TileIndex tile;
            ^~~~
In file included from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/tile_map.h:14:0,
                 from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/rail_map.h:17,
                 from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/station_map.h:13,
                 from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:12:
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/map_func.h: In function ‘SigSegState UpdateSignalsInBuffer(Owner)’:
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/map_func.h:345:29: warning: ‘dir’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  assert(IsValidDiagDirection(dir));
                             ^
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:478:16: note: ‘dir’ was declared here
  DiagDirection dir;
                ^~~
In file included from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/station_map.h:13:0,
                 from /home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:12:
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/rail_map.h:39:30: warning: ‘tile’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  return (RailTileType)GB(_m[t].m5, 6, 2);
                              ^
/home/user/projects/openttd-jgrpp/OpenTTD-patches/src/signal.cpp:477:12: note: ‘tile’ was declared here
  TileIndex tile;
            ^~~~

Steps to reproduce

Check out master, run cmake with CXXFLAGS='-Og -g'. Note this is the only warning produced.

Notes

I have had a preliminary look at the code, and this appears to be a benign warning; so possibly just initializing the variables appropriately upon declaration is enough to silence it.
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Fix: GCC warns about possibly uninitialized data in signal.cpp techgeeknz/OpenTTD
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@techgeeknz