windows libuv build not optimized

[thestinger]

Just a minor issue to figure out in the future.

[emberian]

Still relevant

[huonw]

Triage visit: appears to still be an issue. The first few lines of output of make -n VERBOSE=1 rt/<platform>/stage0/libuv/libuv.a (with extra line breaks):

i686-pc-mingw32

gcc -I/d/stone/rust-vanilla/src/libuv/include -I/d/stone/rust-vanilla/src/libuv/include/uv-private 
    -g --std=gnu89 -D_WIN32_WINNT=0x0600 -I/d/stone/rust-vanilla/src/libuv/include 
    -I/d/stone/rust-vanilla/src/libuv/include/uv-private  -c 
    -o /d/stone/rust-vanilla/src/libuv/src/win/async.o
    /d/stone/rust-vanilla/src/libuv/src/win/async.c
gcc -I/d/stone/rust-vanilla/src/libuv/include -I/d/stone/rust-vanilla/src/libuv/include/uv-private 
    -g --std=gnu89 -D_WIN32_WINNT=0x0600 -I/d/stone/rust-vanilla/src/libuv/include 
    -I/d/stone/rust-vanilla/src/libuv/include/uv-private  -c
    -o /d/stone/rust-vanilla/src/libuv/src/win/core.o
    /d/stone/rust-vanilla/src/libuv/src/win/core.c
gcc -I/d/stone/rust-vanilla/src/libuv/include -I/d/stone/rust-vanilla/src/libuv/include/uv-private 
    -g --std=gnu89 -D_WIN32_WINNT=0x0600 -I/d/stone/rust-vanilla/src/libuv/include 
    -I/d/stone/rust-vanilla/src/libuv/include/uv-private  -c 
    -o /d/stone/rust-vanilla/src/libuv/src/win/dl.o
    /d/stone/rust-vanilla/src/libuv/src/win/dl.c

x86_64-unknown-linux-gnu

gcc --std=c89 -pedantic -Wall -Wextra -Wno-unused-parameter -D_GNU_SOURCE 
    -I/home/huon/rust/src/libuv/include -I/home/huon/rust/src/libuv/include/uv-private 
    -I/home/huon/rust/src/libuv/src -D_LARGEFILE_SOURCE 
    -D_FILE_OFFSET_BITS=64 -DRUST_DEBUG -fno-omit-frame-pointer 
    -DUSE_UTF8 -O2 -m64 -fPIC  -c /home/huon/rust/src/libuv/src/unix/async.c 
    -o src/unix/async.o
gcc --std=c89 -pedantic -Wall -Wextra -Wno-unused-parameter -D_GNU_SOURCE
    -I/home/huon/rust/src/libuv/include -I/home/huon/rust/src/libuv/include/uv-private
    -I/home/huon/rust/src/libuv/src -D_LARGEFILE_SOURCE 
    -D_FILE_OFFSET_BITS=64 -DRUST_DEBUG -fno-omit-frame-pointer
    -DUSE_UTF8 -O2 -m64 -fPIC  -c /home/huon/rust/src/libuv/src/unix/core.c
    -o src/unix/core.o
gcc --std=c89 -pedantic -Wall -Wextra -Wno-unused-parameter -D_GNU_SOURCE
    -I/home/huon/rust/src/libuv/include -I/home/huon/rust/src/libuv/include/uv-private
    -I/home/huon/rust/src/libuv/src -D_LARGEFILE_SOURCE
    -D_FILE_OFFSET_BITS=64 -DRUST_DEBUG -fno-omit-frame-pointer
    -DUSE_UTF8 -O2 -m64 -fPIC  -c /home/huon/rust/src/libuv/src/unix/dl.c
    -o src/unix/dl.o

The flags are extremely different for the former: it appears that none of our CFLAGS get passed to libuv.

Also, as @klutzy points out, there's a FIXME in rt.mk:

# FIXME: For some reason libuv's makefiles can't figure out the
# correct definition of CC on the mingw I'm using, so we are
# explicitly using gcc. Also, we have to list environment variables
# first on windows... mysterious

[klutzy]

The issue occurs on windows only because CFLAGS are passed on other platforms:
#6176 added CFLAGS for all platforms but due to regression issues (#6253 #6279) windows stuff was removed by #6295.
$(CC) is also not explicitly passed on windows. It's the answer for FIXME.

Currently we pass CC and CFLAGS to libuv/Makefile explicitly (from mk/rt.mk):

    $$(Q)$$(MAKE) -C $$(S)src/libuv/ \
        CFLAGS="$$(CFG_GCCISH_CFLAGS) $$(LIBUV_FLAGS_$$(HOST_$(1))) $$(SNAP_DEFINES)" \
        LDFLAGS="$$(CFG_GCCISH_LINK_FLAGS) $$(LIBUV_FLAGS_$$(HOST_$(1)))" \
        CC="$$(CC_$(1))" \
        CXX="$$(CXX_$(1))" \
        AR="$$(AR_$(1))" \
        builddir_name="$$(CFG_BUILD_DIR)/rt/$(1)/stage$(2)/libuv" \
        V=$$(VERBOSE)

However, this prevents any redefinition of CFLAGS in libuv's Makefile: any CFLAGS=... or CFLAGS+=... are ignored if CFLAGS=... is passed by argument.

Yes, it can be problematic for any platform, but regression was only fatal on windows. It's because libuv has two sub makefiles named config-mingw.mk and config-unix.mk and they differ greatly.
config-mingw.mk has

CFLAGS=$(CPPFLAGS) -g --std=gnu89 -D_WIN32_WINNT=0x0600

where CPPFLAGS += -I$(SRCDIR)/include -I$(SRCDIR)/include/uv-private (libuv/build.mk). Since the line was ignored, include paths became wrong. (Also note that CFLAGS is just defined, not appended)

By contrast, config-unix.mk only contains CFLAGS += -g. You can see @huonw's result so that there's no "-g" on linux.
There may be more lurking issues due to this.

The simplest solution is adding override keyword at config-*.mk and replacing "=" with "+=" at config-mingw.mk e.g.:

override CFLAGS+=$(CPPFLAGS) -g --std=gnu89 -D_WIN32_WINNT=0x0600

I guess there exists a better solution but don't know :)