Tk Source Code

File macosx/tkMacOSXXStubs.c
line 178  
#if MAC_OS_X_VERSION_MIN_REQUIRED < 1080

needs to be changed (back, as in 8.6.7) to 
#if MAC_OS_X_VERSION_MIN_REQUIRED < 10100

or build on macOS 10.9.5 will fail with following error:

==> Downloading https://downloads.sourceforge.net/project/tcl/Tcl/8.6.8/tk8.6.8-src.tar.gz
Already downloaded: /Users/mark/Library/Caches/Homebrew/tcl-tk--tk-8.6.8.tar.gz
==> ./configure --prefix=/usr/local/Cellar/tcl-tk/8.6.8 --mandir=/usr/local/Cellar/tcl-tk/8.6.8/share/man --enable-threads --enable-64bit --enable-aqua=yes --without-x --with-tcl=/usr/local/Cellar/tcl-tk/8.
==> make
Last 15 lines from /Users/mark/Library/Logs/Homebrew/tcl-tk/06.make:
        NSOperatingSystemVersion systemVersion = [[NSProcessInfo processInfo] operatingSystemVersion];
        ^
clang -c -Os -pipe  -arch x86_64   -Wall -fno-common -DBUILD_tk -I/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../unix -I/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../generic -I/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../bitmaps -I/private/tmp/tcl-tk-20180316-57034-8xz4cf/tcl8.6.8/generic -I/private/tmp/tcl-tk-20180316-57034-8xz4cf/tcl8.6.8/unix -I/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../macosx -I/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../xlib -DPACKAGE_NAME=\"tk\" -DPACKAGE_TARNAME=\"tk\" -DPACKAGE_VERSION=\"8.6\" -DPACKAGE_STRING=\"tk\ 8.6\" -DPACKAGE_BUGREPORT=\"\" -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DUSE_THREAD_ALLOC=1 -D_REENTRANT=1 -D_THREAD_SAFE=1 -DHAVE_PTHREAD_ATTR_SETSTACKSIZE=1 -DHAVE_PTHREAD_ATFORK=1 -DTCL_THREADS=1 -DMODULE_SCOPE=extern\ __attribute__\(\(__visibility__\(\"hidden\"\)\)\) -DHAVE_HIDDEN=1 -DMAC_OSX_TCL=1 -DHAVE_COREFOUNDATION=1 -DTCL_CFG_DO64BIT=1 -DHAVE_CAST_TO_UNION=1 -DTCL_SHLIB_EXT=\".dylib\" -DNDEBUG=1 -DTCL_CFG_OPTIMIZED=1 -DTCL_WIDE_INT_IS_LONG=1 -DHAVE_SYS_TIME_H=1 -DTIME_WITH_SYS_TIME=1 -DHAVE_INTPTR_T=1 -DHAVE_UINTPTR_T=1 -DHAVE_PW_GECOS=1 -DHAVE_AVAILABILITYMACROS_H=1 -DHAVE_WEAK_IMPORT=1 -D_DARWIN_C_SOURCE=1 -DMAC_OSX_TK=1      -DTCL_NO_DEPRECATED -std=gnu99 -x objective-c  -mdynamic-no-pic /private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../unix/tkAppInit.c
/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../macosx/tkMacOSXXStubs.c:184:10: error: use of undeclared identifier 'systemVersion'
        major = systemVersion.majorVersion;
                ^
/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../macosx/tkMacOSXXStubs.c:185:10: error: use of undeclared identifier 'systemVersion'
        minor = systemVersion.minorVersion;
                ^
/private/tmp/tcl-tk--tk-20180316-57034-1ofgo0n/tk8.6.8/unix/../macosx/tkMacOSXXStubs.c:186:10: error: use of undeclared identifier 'systemVersion'
        patch = systemVersion.patchVersion;
                ^
4 errors generated.
make: *** [tkMacOSXXStubs.o] Error 1
make: *** Waiting for unfinished jobs....

Closing: the fix suggested here was made in [6c6235b3f1] and appeared in 8.6.9.1 (although the relevant line has since been revised).