[CMake] LINK_LIBRARIES not spilled to response file

[Zaheer Chothia]

Hello,

I encountered an issue while building a CMake project where one target is linked
against a large number of libraries.  Unlike object files, libraries are not
placed into a response file, which can lead to build commands which exceed the
length limits on Windows.  For reference, I am using the CMake 2.8.9-rc1 and
Ninja generator with Microsoft compilers.

Following this mail is a testcase generator [1] to demonstrate this issue
(sample project attached for convenience).  The build fails with this error (for
readibility I replaced a long sequence of libraries with <...>):

    FAILED: cmd.exe /c cd. && "C:\Program Files
(x86)\CMake\bin\cmake.exe" -E vs_link_exe
C:\PROGRA~2\MICROS~3.0\VC\bin\cl.exe  /nologo @hello.exe.rsp  /DWIN32
/D_WINDOWS /W3 /Zm1000 /D_DEBUG /MDd /Zi  /Ob0 /Od /RTC1 /Fehello.exe
/Fdhello.pdb -link /implib:hello.lib /version:0.0  /STACK:10000000
/machine:X86  /debug /INCREMENTAL /subsystem:console
src\abcdefghijklmnopqrstuvwxyz0123456789\library1.lib
src\abcdefghijklmnopqrstuvwxyz0123456789\library2.lib <...>
kernel32.lib user32.lib gdi32.lib winspool.lib shell32.lib ole32.lib
oleaut32.lib uuid.lib comdlg32.lib advapi32.lib && cd.
    The command line is too long.

    ninja: build stopped: subcommand failed.

Although this example may seem artificial, with the use case I refer to (i)
libraries are are specified by absolute paths so they are indeed reasonably long
and (ii) since there are third-party libraries involved I would not be able to
simply combine source files into one large library as is possible here.  I
should also mention that this issue does not affect the Visual Studio
generators, however it is present with the following: Ninja, MinGW
Makefiles, NMake Makefiles, MSYS Makefiles.  For Ninja I suspect that the
indirection via cmd.exe imposes a maximum command length of 8192 KB, whereas for
the others this will likely be 32 KB (CreateProcess).

I would be quite content if this is fixed for the Ninja generator.  A simple fix
would be to adapt the build rules by moving $LINK_LIBRARIES from 'command' to
'rspfile_content':

    --- rules.ninja.bak	2012-06-28 15:23:35 +0100
    +++ rules.ninja	2012-06-28 15:38:09 +0100
    @@ -40,10 +40,10 @@
     # Rule for linking C executable.

     rule C_EXECUTABLE_LINKER_RSPFILE
    -  command = cmd.exe /c $PRE_LINK && "C:\Program Files
(x86)\CMake\bin\cmake.exe" -E vs_link_exe
C:\PROGRA~2\MICROS~3.0\VC\bin\cl.exe  /nologo @$out.rsp  $FLAGS
/Fe$out /Fd$TARGET_PDB -link /implib:$TARGET_IMPLIB /version:0.0
$LINK_FLAGS $LINK_LIBRARIES && $POST_BUILD
    +  command = cmd.exe /c $PRE_LINK && "C:\Program Files
(x86)\CMake\bin\cmake.exe" -E vs_link_exe
C:\PROGRA~2\MICROS~3.0\VC\bin\cl.exe  /nologo @$out.rsp  $FLAGS
/Fe$out /Fd$TARGET_PDB -link /implib:$TARGET_IMPLIB /version:0.0
$LINK_FLAGS && $POST_BUILD
       description = Linking C executable $out
       rspfile = $out.rsp
    -  rspfile_content = $in
    +  rspfile_content = $in $LINK_LIBRARIES

Best,

--Zaheer

---- [1]: BEGIN: testcase.sh ---------------------------------------------------
#!/bin/bash -e

NUM_LIBRARIES=500
# Use a long path to quickly exhaust the command-line length limit.
SRC_DIR=src/abcdefghijklmnopqrstuvwxyz0123456789

# Root directory: application and CMakeLists.txt
echo "int main() { return 0; }" > hello.c

cat << EOF > CMakeLists.txt
cmake_minimum_required(VERSION 2.8)

project(Hello)

add_subdirectory($SRC_DIR)

add_executable(hello hello.c)
target_link_libraries(hello
EOF

for ((i = 1; i <= $NUM_LIBRARIES; i++)); do
    echo "    library$i" >> "CMakeLists.txt"
done

echo ")" >> "CMakeLists.txt"

# Libraries: sources and CMakeLists.txt
mkdir -p "$SRC_DIR"
[[ -f "$SRC_DIR/CMakeLists.txt" ]] && rm "$SRC_DIR/CMakeLists.txt"
for ((i = 1; i <= $NUM_LIBRARIES; i++)); do
    echo "int function$i() { return $i; }" > "$SRC_DIR/function$i.c"
    echo "add_library(library$i function$i.c)" >> "$SRC_DIR/CMakeLists.txt"
done

echo "Testcase has been setup: now build with CMake and Ninja generator."
---- [1]: END: testcase.sh ---------------------------------------------------
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