From 78c66b37266707a3cf2904c3891b08cddae8d83e Mon Sep 17 00:00:00 2001 From: Andreas Schuh Date: Fri, 25 Nov 2016 18:09:44 +0000 Subject: [PATCH] doc: Add section on how to use gflags with Bazel --- index.html | 57 ++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 49 insertions(+), 8 deletions(-) diff --git a/index.html b/index.html index d3aee33..5dcc4b6 100644 --- a/index.html +++ b/index.html @@ -39,7 +39,8 @@
Table of contents
Introduction
Download and Installation
-
Linking to gflags using CMake
+
Declare dependency on gflags with CMake
+
Declare dependency on gflags with Bazel
DEFINE: Defining Flags In Program
Accessing the Flag
DECLARE: Using the Flag in a Different File
@@ -101,9 +102,14 @@ You can clone the project using the command:

    git clone https://github.com/gflags/gflags.git
-

Build and installation instructions are provided in the INSTALL file.

+

Build and installation instructions are provided in the +INSTALL file. +The installation of the gflags package includes configuration files for popular build systems +such as pkg-config, +CMake, and Bazel.

-

Linking to gflags using CMake

+ +

Declare dependency on gflags with CMake

Using gflags within a project which uses CMake 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:

target_link_libraries(foo gflags) +

Declare dependency on gflags with Bazel

+ +

To use gflags within a project which uses Bazel as build tool, +add the following lines to your WORKSPACE file +(see also Bazel documentation of git_repository): + +

+git_repository(
+    name   = "com_github_gflags_gflags",
+    commit = "<INSERT COMMIT SHA HERE>",
+    remote = "https://github.com/gflags/gflags.git",
+)
+
+bind(
+    name = "gflags",
+    actual = "@com_github_gflags_gflags//:gflags",
+)
+
+ +

You can then add //external:gflags to the deps section of a cc_binary +or cc_library rule, and #include "gflags/gflags.h" to include it in your source code.

+ +

For example, see the following BUILD rule of the gflags/example project:

+ +
+cc_binary(
+    name = "foo",
+    srcs = ["main.cc"],
+    deps = ["//external:gflags"],
+)
+
+

DEFINE: Defining Flags In Program

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);

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 main().

-

RegisterFlagValidator() returns true if the -registration is successful. It return false if the registration fails +

The above used DEFINE_validator macro calls the +RegisterFlagValidator() 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.

+b) a different validator has already been registered for this flag. +The return value is available as global static boolean variable named +<flag>_validator_registered.

Putting It Together: How to Set Up Flags