Building q3_ui wil fail and break the entire build process if you build a branch with the cURL issue (https://bugzilla.icculus.org/show_bug.cgi?id=6086) patched due to a strange macro issue:

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UI_CC code/q3_ui/ui_main.c
<command-line>:0:4: error: expected identifier or '(' before numeric constant
code/q3_ui/../qcommon/q_shared.h:190:15: note: in expansion of macro 'ui'
  unsigned int ui;
               ^
In file included from code/q3_ui/ui_local.h:26:0,
                 from code/q3_ui/ui_main.c:32:
code/q3_ui/../qcommon/q_shared.h:191:1: warning: no semicolon at end of struct o
r union [enabled by default]
 } floatint_t;
 ^

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This is because the union uses "ui" as a member which is somehow defined as a macro in the build process. I have not been able to locate the definition of the ui macro. I have attempted searching for it using grep and listing all GCC predefinitions (gcc -dM -E - < /dev/null). It is not in the Makefile either.

The error does not occur on Ubuntu, OSX or if I use CC=clang in MinGW.

Adding this in q_shared.h before the union declaration resolves the issue:

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#ifdef ui
#undef ui
#endif

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It can also potentially be fixed by refactoring the union member variable's name.

Other resources regarding this topic:
 - http://community.ioquake.org/t/building-ioquake3-using-mingw-on-windows-7-fails/198
 - http://openarena.ws/board/index.php?topic=4925.msg50279