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+# rc
+
+This contains a cross-platform reimplementation of rc.exe.
+
+This exists mainly to compile .rc files on non-Windows hosts for cross builds.
+However, it also runs on Windows for two reasons:
+
+1. To compare the output of Microsoft's rc.exe and the reimplementation and to
+    check that they produce bitwise identical output.
+2. The reimplementation supports printing resource files in /showIncludes
+   output, which helps getting build dependencies right.
+
+The resource compiler consists of two parts:
+
+1. A python script rc.py that serves as the driver.  It does unicode
+   conversions, runs the input through the preprocessor, and then calls the
+   actual resource compiler.
+2. The resource compiler, a C++ binary obtained via sha1 files from Google
+   Storage.  The binary's code currenty lives at
+   https://github.com/nico/hack/tree/master/res, even though work is (slowly)
+   underway to upstream it into LLVM.
+
+To update the rc binary, run `upload_rc_binaries.sh` in this directory, on a
+Mac.
+
+rc isn't built from source as part of the regular chrome build because
+it's needed in a gn toolchain tool, and these currently cannot have deps.
+Alternatively, gn could be taught about deps on tools, or rc invocations could
+be not a tool but a template like e.g. yasm invocations (which can have deps),
+then the prebuilt binaries wouldn't be needed.