Kept warnings

You may have had the experience of running a long build, and noticed some compiler warnings early in the build that have long since scrolled off the screen. How to get those warnings without cleaning and rerunning the build?

One innovative feature of tmake is that it saves any build warnings (stderr output) in the build cache and can redisplay those warnings with 'tmake --warnings'.

The --warnings options tells tmake to perform the build as normal, but for each target that is up-to-date, if any warnings were previously captured, the build message and warnings are displayed as though command were being rerun (although it isn't). For example, consider a build of lua 5.3.2 ported to tmake.

$ tmake --warnings
    Cc           src/lundump.o
src/lundump.c:237:33: warning: adding 'int' to a string does not append to the string [-Wstring-plus-int]
  checkliteral(S, LUA_SIGNATURE + 1, "not a");  /* 1st char already checked */
                  ~~~~~~~~~~~~~~^~~
src/lundump.c:237:33: note: use array indexing to silence this warning
  checkliteral(S, LUA_SIGNATURE + 1, "not a");  /* 1st char already checked */
                                ^
                  &             [  ]
1 warning generated.

This can be very useful with the "quickfix" feature to jump to errors from within the vi/vim editor.