### Do not break Quake or its mods, and any other game using the engine.

The engine has known compatibility issues with Quake and many community mods. All code must not make the situation worse. This is analogous to the policy of the Linux kernel to not break userspace.

### Sign off all of your commits if they are to be included upstream.

You must use a valid, permanent email address.

1. In statements, the curly brace should be placed on the next line at the same indentation level as the statement. If the statement only involves a single line, do not use curly braces.

   ```c // Example: if(foo == 1) { Do_Something(); Do_Something_Else(); } else Do_Something_Else_Else();

   if(bar == 1) Do_Something_Else_Else_Else(); ```

2. Use tabs for indentation.

   Use spaces subsequently for alignment of the parameters of multi-line function calls or declarations, or statements.

   c // Example: if(very_long_statement && very_long_statement_aligned && foo) { if(indented) { Do_Something(); Do_Something_Else(); } }

3. If possible, try to keep individual lines of code less than 100 characters.

4. Pointer operators should be placed on the right-hand side.

   c int foo = 1; int *bar = &foo;

5. Type casts should have a space between the type and the pointer.

   c int *foo = (int *)malloc(5);

6. Use spaces after each comma when listing parameters or variables of a struct.

7. Multi-line comments should be formatted like so:

   c /*

   • This is a multi-line comment.
   • Sometimes, I dream about cheese. */

   But this is okay too:

   c /* This is another multi-line comment.

   • Hiya! How are you? */

8. If following these guidelines in any manner would make any code less readable or harder to follow, ignore them. This section is only guidelines, not rules. We're not gonna beat you over the head in pull requests because you misplaced a dereference operator.

   For example, in some situations, placing the block on the same line as the condition would be okay because it looks cleaner:

   c if (foo) Do_Something(); if (bar) Do_Something_Else(); if (far) near(); if (boo) AHH("!!!\n");

DarkPlaces is written in the common subset of C and C++. This means it is (usually) both valid C and C++. We historically wanted to keep it that way, but don't worry about it unless you care enough and/or are a maintainer.

Most of the differences are caught by -Wc++-compat but some are subtle and would cause behavior differences between the two compilers, or are not caught by that warning. The things to look out for are:

1. Character constants are int-sized in C but char-sized in C++. This means ‘sizeof('a’)` will be 4 in C, but 1 in C++.
2. goto label; cannot jump over a variable initialization. This will cause a compiler error as C++ but is not caught by -Wc++-compat. This is nevertheless bad code, so avoid this anyway.

If, for some reason, you care enough, compatibility can always be tested affirmatively by setting CC=g++. CC=clang++ may not work in the future, if it didn't already stop working in current versions of LLVM, as it otherwise spams deprecation warnings for using a C file as input to a C++ compiler.