b82a8a0925
There's an if-else chain that first deals with figuring out if there's
an entity where your left-click happened, and to do this it uses
edentat(), which returns a sentinel value of -1 if there is NOT an
entity where your cursor is.
It's very important to check that the value returned ISN'T -1 before you
start indexing the 'edentity' vector, since if you DO index it with that
-1, it'll result in Undefined Behavior because you're doing an
out-of-bounds array access.
Now, here's what the if-else chain looked like before:
if(tmp==-1 && ed.free(ed.tilex,ed.tiley)==0)
{
...
}
else if(edentity[tmp].t==1)
The bug here is very subtle but it was an easy oversight. Basically, if
'ed.free' ended up not being zero, control flow would jump to the next
"else if" over, which then ends up asking for the -1th index of
'edentity', which is Undefined Behavior.
This undefined behavior has now resulted in a crash on my system after
TerryCavanagh/VVVVVV#172, due it shuffling things around juuuuust enough
such that this UB would end up resulting in a segfault instead of
chugging along and working fine. For me and my system, this meant that
if my first left-click in the editor upon opening the game was me
placing down a tile and not placing down an entity, the game would
crash. But, it would be fine if I first placed down an entity and then
afterwards placed down tiles, because it's UB.
And I'm almost certain this was the cause of the very strange bug where
you couldn't hold down left-click for the foreground-placing tool (but
you COULD for the background-placing tool) that seemed to occur most
often on Windows (TerryCavanagh/VVVVVV#25).
The solution to this is to stick in another conditional in the tree
before any indexing occurs, such that there's no way any other
conditionals with the indexing in the conditional tree could end up
being hit. In summary, the if-else chain looks like this now:
if(tmp==-1 && ed.free(ed.tilex,ed.tiley)==0)
{
...
}
else if(tmp == -1)
{
//Important! Do nothing, or else Undefined Behavior will happen
}
else if(edentity[tmp].t==1)
|
||
|---|---|---|
| .. | ||
| src | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CONTRIBUTORS.txt | ||
| README.md | ||
How to Build
VVVVVV's official desktop versions are built with the following environments:
- Windows: Visual Studio 2010
- macOS: Xcode CLT, currently targeting 10.9 SDK
- GNU/Linux: CentOS 7
The engine depends solely on SDL2 and SDL2_mixer. All other dependencies are statically linked into the engine. The development libraries for Windows can be downloaded from their respective websites, Linux developers can find the dev libraries from their respective repositories, and macOS developers should compile and install from source (including libogg/libvorbis/libvorbisfile).
Steamworks support is included and the DLL is loaded dynamically, you do not need the SDK headers and there is no special Steam or non-Steam version. The current implementation has been tested with Steamworks SDK v1.46.
To generate the projects on Windows:
# Put your SDL2/SDL2_mixer folders somewhere nice!
mkdir flibitBuild
cd flibitBuild
cmake -G "Visual Studio 10 2010" .. -DSDL2_INCLUDE_DIRS="C:\SDL2-2.0.10\include;C:\SDL2_mixer-2.0.4\include" -DSDL2_LIBRARIES="C:\SDL2-2.0.10\lib\x86\SDL2;C:\SDL2-2.0.10\lib\x86\SDL2main;C:\SDL2_mixer-2.0.4\lib\x86\SDL2_mixer"
Note that on some systems, the SDL2_LIBRARIES list on Windows may need
SDL2/SDL2main/SDL2_mixer to have .lib at the end of them. The reason for this
inconsistency is unknown.
To generate everywhere else:
mkdir flibitBuild
cd flibitBuild
cmake ..
macOS may be fussy about the SDK version. How to fix this is up to the whims of however Apple wants to make CMAKE_OSX_SYSROOT annoying to configure and retain each time Xcode updates.
Including data.zip
You'll need the data.zip file from VVVVVV to actually run the game! It's available to download separately for free in the Make and Play edition of the game. Put this file next to your executable and the game should run.
This is intended for personal use only - our license doesn't allow you to actually distribute this data.zip file with your own forks without getting permission from us first. See LICENSE.md for more details. (If you've got a project in mind that requires distributing this file, get in touch!)
A Word About Compiler Quirks
This engine is super fussy about optimization levels and runtime checks. In particular, the Windows version absolutely positively must be compiled in Debug mode, with /RTC enabled. If you build in Release mode, or have /RTC disabled, the game behaves dramatically different in ways that were never fully documented (bizarre softlocks, out-of-bounds issues that don't show up in tools like Valgrind, stuff like that). There are lots of things about this old code that could be cleaned up, polished, rewritten, and so on, but this is the one that will probably bite you the hardest when setting up your own build, regardless of platform.
We hope you'll enjoy messing with the source anyway!
Love, flibit