Examples

Every Native Client SDK bundle comes with a folder of example applications. Each example demonstrates one or two key Native Client programming concepts. After you’ve downloaded the SDK, follow the instructions on this page to build and run the examples.

Your version of Chrome must be equal to or greater than the version of your SDK bundle. For example, if you’re developing with the pepper_35 bundle, you must use Google Chrome version 35 or greater. To find out what version of Chrome you’re using, type about:chrome or about:version in the Chrome address bar.

Build the SDK examples

The Makefile scripts for the SDK examples can build multiple versions of the examples using any of the three SDK toolchains (newlib, glibc, and PNaCl) and in both release and debug configurations. Note that some examples, dlopen for example, build only with particular toolchains.

Find the toolchains for each example by looking at the VALID_TOOLCHAINS variable in the Makefile for a particular example. The first item listed is the default. It’s built when you run an example make file without parameters. for example running make in the core directory of pepper_35 builds the example using the newlib toolchain.

$ cd pepper_35/examples/api/core
$ make
  CXX  newlib/Release/core_x86_32.o
  LINK newlib/Release/core_unstripped_x86_32.nexe
  VALIDATE newlib/Release/core_unstripped_x86_32.nexe
  CXX  newlib/Release/core_x86_64.o
  LINK newlib/Release/core_unstripped_x86_64.nexe
  VALIDATE newlib/Release/core_unstripped_x86_64.nexe
  CXX  newlib/Release/core_arm.o
  LINK newlib/Release/core_unstripped_arm.nexe
  VALIDATE newlib/Release/core_unstripped_arm.nexe
  STRIP newlib/Release/core_x86_32.nexe
  STRIP newlib/Release/core_x86_64.nexe
  STRIP newlib/Release/core_arm.nexe
  CREATE_NMF newlib/Release/core.nmf

As you can see, this produces a number of architecture specific nexe files in the pepper_35/examples/api/core/Release directory. Create debug versions by using the CONFIG parameter of the make command.

$make CONFIG=Debug

This creates similar output, but in pepper_35/examples/api/core/Debug.

Select a different toolchain with the TOOLCHAIN parameter. For example:

$ cd pepper_35/examples/api/core
$ make TOOLCHAIN=pnacl CONFIG=Release
  CXX  pnacl/Release/core.o
  LINK pnacl/Release/core_unstripped.bc
  FINALIZE pnacl/Release/core_unstripped.pexe
  CREATE_NMF pnacl/Release/core.nmf

You can also set TOOLCHAIN to all to build all Release versions with default toolchains.

$ cd pepper_35/examples/api/core
$ make TOOLCHAIN=all
make TOOLCHAIN=newlib
make[1]: Entering directory 'pepper_35/examples/api/core'
  CXX  newlib/Release/core_x86_32.o
  LINK newlib/Release/core_unstripped_x86_32.nexe
  VALIDATE newlib/Release/core_unstripped_x86_32.nexe
  CXX  newlib/Release/core_x86_64.o
  LINK newlib/Release/core_unstripped_x86_64.nexe
  VALIDATE newlib/Release/core_unstripped_x86_64.nexe
  CXX  newlib/Release/core_arm.o
  LINK newlib/Release/core_unstripped_arm.nexe
  VALIDATE newlib/Release/core_unstripped_arm.nexe
  STRIP newlib/Release/core_x86_32.nexe
  STRIP newlib/Release/core_x86_64.nexe
  STRIP newlib/Release/core_arm.nexe
  CREATE_NMF newlib/Release/core.nmf
make[1]: Leaving directory 'pepper_35/examples/api/core'
make TOOLCHAIN=glibc
make[1]: Entering directory 'pepper_35/examples/api/core'
  CXX  glibc/Release/core_x86_32.o
  LINK glibc/Release/core_unstripped_x86_32.nexe
  VALIDATE glibc/Release/core_unstripped_x86_32.nexe
  CXX  glibc/Release/core_x86_64.o
  LINK glibc/Release/core_unstripped_x86_64.nexe
  VALIDATE glibc/Release/core_unstripped_x86_64.nexe
  ...
  (content excerpted)
  ...

Build results

After running make, example directories will contain one or more of the following subdirectories, depending on which Makefile you run:

  • newlib with subdirectories Debug and Release;
  • glibc with subdirectories Debug and Release;
  • pnacl with subdirectories Debug and Release;

For the newlib and glibc toolchains the Debug and Release subdirectories contain .nexe files for all target architectures. For the PNaCl toolchain they contain a single .pexe file. PNaCl debug also produces pre-translated .nexe files, for ease of debugging. All Debug and Release directories contain a manifest (.nmf) file that references the associated .nexe or .pexe files. For information about Native Client manifest files, see the Technical Overview.

For details on how to use make, see the GNU ‘make’ Manual. For details on how to use the SDK toolchain itself, see Building Native Client Modules.

Run the SDK examples

Disable the Chrome cache

Chrome’s intelligent caching caches resources aggressively. When building a Native Client application you should disable the cache to make sure that Chrome loads the latest version. Intelligent caching only remains inactive while Developer Tools are open. Otherwise, agressive caching continues.

  1. Open Chrome’s developer tools by clicking the menu icon menu-icon and choosing Tools > Developer tools.
  2. Click the gear icon gear-icon in the bottom right corner of the Chrome window.
  3. Under the “General” settings, check the box next to “Disable cache”.

Run the examples

To run the SDK examples, use the make run command:

$ cd pepper_35/examples/api/core
$ make run

This launches a local HTTP server that serves the example. It then launches Chrome with the address of this server, usually http://localhost:5103. After you close Chrome, the local HTTP server automatically shuts down.

This command tries to find an executable named google-chrome in your PATH environment variable. If it can’t, you’ll get an error message like this:

pepper_35/tools/common.mk:415: No valid Chrome found at CHROME_PATH=
pepper_35/tools/common.mk:415: *** Set CHROME_PATH via an environment variable, or command-line..  Stop.

Add an environment variable for Chrome

Set the CHROME_PATH environment variable to the location of your Chrome executable.

  • On Windows:

    The default install location of Chrome is C:\Program Files (x86)\Google\Chrome\Application\chrome.exe for Chrome stable and C:\Users\<username>\AppData\Local\Google\Chrome SxS\Application\chrome.exe for Chrome Canary. Try looking in those directories first:

    > set CHROME_PATH=<Path to chrome.exe>
    
  • On Linux:

    $ export CHROME_PATH=<Path to google-chrome>
    
  • On Mac:

    The default install location of Chrome is /Applications/Google Chrome.app/Contents/MacOS/Google Chrome for Chrome Stable and Applications/Google Chrome Canary.app/Contents/MacOS/Google Chrome Canary for Chrome Canary. Note that you have to reference the executable inside the application bundle, not the top-level .app directory:

    $ export CHROME_PATH=<Path to Google Chrome>
    

Run the SDK examples as Chrome apps

Each example can also be launched as a Chrome apps. A Chrome app is a special zip file (with a .crx extension) hosted in the Chrome Web Store. This file contains all of the application parts: A Chrome Web Store manifest file (manifest.json), an icon, and all of the regular Native Client application files. Refer to What are Chrome Apps for more information about creating a Chrome app.

Some Pepper features, such as TCP or UDP socket access, are only allowed in Chrome apps. The examples that use these features must be run as Chrome apps, by using the following command:

$ make run_package

You can use TOOLCHAIN and CONFIG parameters as described above to run with a different toolchain or configuration.

Debugging the SDK examples

The NaCl SDK uses GDB to debug Native Client code. The SDK includes a prebuilt version of GDB that is compatible with NaCl code. To use it, run the make debug command from an example directory:

$ make debug

This launches Chrome with the --enable-nacl-debug flag set. This flag causes Chrome to pause when a NaCl module is first loaded, waiting for a connection from gdb. The make debug command also simultaneously launches GDB and loads the symbols for that NEXE. To connect GDB to Chrome, in the GDB console, type:

(gdb) target remote :4014

This tells GDB to connect to a TCP port on localhost:4014, the port that Chrome is listening on. GDB will respond:

Remote debugging using :4014
0x000000000fa00080 in ?? ()

At this point, you can use the standard GDB commands to debug your NaCl module. The most common commands you will use to debug are continue, step, next, break and backtrace. See Debugging for more information about debugging a Native Client application.