Allow building with cmake (to ease building on windows)

[trondn]

The patch series allows for building on windows with the following steps:

git clone git://github.com/trondn/snappy
mkdir build
cd build
cmake -G "NMake Makefiles" ..\snappy
nmake all test

(It should also build on unix systems by dropping the "-G NMake Makefiles" part)

[Optiligence]

Just my 2 cents when i see this:
https://cmake.org/cmake/help/v3.4/module/GenerateExportHeader.html
https://cmake.org/cmake/help/v3.4/module/CMakePackageConfigHelpers.html (omitting this disregards an integral part of the cmake ecosystem)
for the vs compile fix see #10

[trondn]

I've never used the GenerateExportHeader or PackageConfig thing before :-) Updated the set to use that

[Nulifier]

Your config.h.in file doesn't work for MSVC 2015. You need to either check for _MSC_VER <= 1900 or increment it as it still doesn't have ssize_t.

[jakirkham]

Would be great if this works on VS 2008 also.

[ccleve]

I cloned today's version of google/snappy and applied this pull request to it. It built fine and the unit tests ran fine as well. I'm on Windows 10 with Visual Studio 14. There were a few compile warnings (attached).

If the warnings are not of concern, then please accept this PR. It'll make building projects that depend on snappy easier.
warnings.txt

[rapoth]

@trondn Thank you for submitting this PR! I can confirm this works on today's version of google/snappy with similar warnings with Visual Studio 14 2015 on Windows 10.

When I run the unit tests, I get a warning:

Running microbenchmarks.
WARNING: Compiled without optimization, will be slow.

Do you by any chance happen to know why?

[vrabaud]

Looks pretty good to me !

[vrabaud]

That variable is useless now that you use SNAPPY_MAJOR in SET_TARGET_PROPERTIES.

[vrabaud]

The project is CXX only no ?

[alkis]

We export a C only API by wrapping the C++ code. See snappy-c.h.

[vrabaud]

typo: Building

[vrabaud]

That should probably be its own PR no ? The smaller the PR, the better.

[vrabaud]

The three commits should probably be independent PR, not to lose track of the awesomeness of the CMake commit :)

[vrabaud]

For the warning in VS, maybe you can add something like:

if(NOT CMAKE_BUILD_TYPE)
set(CMAKE_BUILD_TYPE "Release" CACHE
"Build type: Release, Debug or RelWithDebInfo" STRING FORCE
)
endif()

[alkis]

Forgive my Cmake noobishness, but Cmake best practices says do not use include_directories but target_include_directories instead.

[alkis]

target_add_definitions instead?

[alkis]

Is it possible to remove all SNAPPY_PUBLIC_API and use WINDOWS_EXPORT_ALL_SYMBOLS instead?

[jakirkham]

Not to be noisy, but is there any news on this PR?

Edit: I guess the work is continuing in PR ( #29 ).

[alkis]

Closing this because CMake support has been added internally and will be part of the next release.