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doc: Add section on how to use gflags with Bazel

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Andreas Schuh 2016-11-25 18:09:44 +00:00
parent ea1cc83b50
commit 78c66b3726
1 changed files with 49 additions and 8 deletions
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@ -39,7 +39,8 @@
<dt> Table of contents </dt>
<dd> <a href="#intro">Introduction</a> </dd>
<dd> <a href="#download">Download and Installation</a> </dd>
<dd> <a href="#cmake">Linking to gflags using CMake</a></dd>
<dd> <a href="#cmake">Declare dependency on gflags with CMake</a></dd>
<dd> <a href="#bazel">Declare dependency on gflags with Bazel</a></dd>
<dd> <a href="#define">DEFINE: Defining Flags In Program</A> </dd>
<dd> <a href="#using">Accessing the Flag</A> </dd>
<dd> <a href="#declare">DECLARE: Using the Flag in a Different File</a> </dd>
@ -101,9 +102,14 @@ You can clone the project using the command:</p>
<pre>
git clone https://github.com/gflags/gflags.git
</pre>
<p>Build and installation instructions are provided in the <A href="https://github.com/gflags/gflags/blob/master/INSTALL.md">INSTALL</A> file.</p>
<p>Build and installation instructions are provided in the
<A href="https://github.com/gflags/gflags/blob/master/INSTALL.md">INSTALL</A> file.
The installation of the gflags package includes configuration files for popular build systems
such as <A href="https://www.freedesktop.org/wiki/Software/pkg-config/">pkg-config</A>,
<A href="#cmake">CMake</A>, and <A href="#bazel">Bazel</A>.</p>
<h2> <A name=cmake>Linking to gflags </A> using CMake</h2>
<h2> <A name=cmake>Declare dependency on gflags with CMake</A></h2>
<p>Using gflags within a project which uses <A href="http://www.cmake.org">CMake</A> for its build system is easy.
You can either require an external installation of the gflags package and find it using CMake's find_package
@ -141,6 +147,38 @@ imported gflags library target:</p>
target_link_libraries(foo gflags)
</pre>
<h2> <A name=bazel>Declare dependency on gflags with Bazel</A></h2>
<p>To use gflags within a project which uses <A href="https://bazel.build/">Bazel</A> as build tool,
add the following lines to your <code>WORKSPACE</code> file
(see also Bazel documentation of <A href="https://www.bazel.io/versions/master/docs/be/workspace.html#git_repository">git_repository</A>):
<pre>
git_repository(
name = "com_github_gflags_gflags",
commit = "&lt;INSERT COMMIT SHA HERE&gt;",
remote = "https://github.com/gflags/gflags.git",
)
bind(
name = "gflags",
actual = "@com_github_gflags_gflags//:gflags",
)
</pre>
<p>You can then add <code>//external:gflags</code> to the <code>deps</code> section of a <code>cc_binary</code>
or <code>cc_library</code> rule, and <code>#include "gflags/gflags.h"</code> to include it in your source code.</p>
<p>For example, see the following <code>BUILD</code> rule of the gflags/example project:</p>
<pre>
cc_binary(
name = "foo",
srcs = ["main.cc"],
deps = ["//external:gflags"],
)
</pre>
<h2> <A name=define>DEFINE: Defining Flags In Program</A> </h2>
<p> Defining a flag is easy: just use the appropriate macro for the
@ -284,17 +322,20 @@ static bool ValidatePort(const char* flagname, int32 value) {
return false;
}
DEFINE_int32(port, 0, "What port to listen on");
static const bool port_dummy = RegisterFlagValidator(&FLAGS_port, &ValidatePort);
DEFINE_validator(port, &ValidatePort);
</pre>
<p>By doing the registration at global initialization time (right
after the DEFINE), we ensure that the registration happens before
after the DEFINE_int32), we ensure that the registration happens before
the commandline is parsed at the beginning of <code>main()</code>.</p>
<p><code>RegisterFlagValidator()</code> returns true if the
registration is successful. It return false if the registration fails
<p>The above used <code>DEFINE_validator</code> macro calls the
<code>RegisterFlagValidator()</code> function which returns true if the
registration is successful. It returns false if the registration fails
because a) the first argument does not refer to a commandline flag, or
b) a different validator has already been registered for this flag.</p>
b) a different validator has already been registered for this flag.
The return value is available as global static boolean variable named
<code>&lt;flag&gt;_validator_registered</code>.</p>
<h2> <A name=together>Putting It Together: How to Set Up Flags</A> </h2>