modern-cmake/chapters/projects/download.md

# Downloading Projects

## Downloading Method: build time

Until CMake 3.11, the primary download method for packages was done at build time. This causes several issues; most important of which is that `add_subdirectory` doesn't work on a file that doesn't exist yet! The built-in tool for this, ExternalProject, has to work around this by doing the build itself. (It can, however, build non-CMake packages as well).[^1]

[^1]: Note that ExternalData is the tool for non-package data.

## Downloading Method: configure time

If you prefer configure time, see the [Crascit/DownloadProject](https://github.com/Crascit/DownloadProject) repository for a drop-in solution. Submodules work so well, though, that I've discontinued most of the downloads for things like GoogleTest and moved them to submodules. Auto downloads are harder to mimic if you
don't have internet access, and they are often implemented in the build directory, wasting time and space if you have multiple build directories.
Misc touch-ups 2020-06-09 14:59:07 +00:00			`# Downloading Projects`
Reordering and moving things around 2018-03-29 19:30:00 +02:00
Adding catch and some fixes 2018-03-30 15:15:37 +02:00			`## Downloading Method: build time`
Reordering and moving things around 2018-03-29 19:30:00 +02:00
Misc touch-ups 2020-06-09 14:59:07 +00:00			Until CMake 3.11, the primary download method for packages was done at build time. This causes several issues; most important of which is that `add_subdirectory` doesn't work on a file that doesn't exist yet! The built-in tool for this, ExternalProject, has to work around this by doing the build itself. (It can, however, build non-CMake packages as well).[^1]
Reordering and moving things around 2018-03-29 19:30:00 +02:00
Adding catch and some fixes 2018-03-30 15:15:37 +02:00			`[^1]: Note that ExternalData is the tool for non-package data.`
Reordering and moving things around 2018-03-29 19:30:00 +02:00
Adding catch and some fixes 2018-03-30 15:15:37 +02:00			`## Downloading Method: configure time`
Reordering and moving things around 2018-03-29 19:30:00 +02:00
Adding catch and some fixes 2018-03-30 15:15:37 +02:00			`If you prefer configure time, see the [Crascit/DownloadProject](https://github.com/Crascit/DownloadProject) repository for a drop-in solution. Submodules work so well, though, that I've discontinued most of the downloads for things like GoogleTest and moved them to submodules. Auto downloads are harder to mimic if you`
style: update style 2020-08-03 18:16:52 -04:00			`don't have internet access, and they are often implemented in the build directory, wasting time and space if you have multiple build directories.`