third_party/yasm/README.skia

# Copyright (c) 2012 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

These platform specific Makefiles are necesary to build yasm on different platforms.  The rest of
the yasm code is pulled into externals via the DEPS file.

Chromium builds yasm using the below procedure.  We take a few shortcuts.  We mirror Chromium's
yasm repositories in our DEPS file, and we copy these config files directly from Chromium.

NOTE: We were are currently unable to build yasm for Android on x86 and x86_64.  Instead we are
using a precompiled binary in the config/android directory.
TODO (msarett): Fix this!

Excerpt from [chromium] //src/third_party/yasm/README.chromium:

Instructions for recreating the yasm.gyp file.
  1) Get a clean version of the yasm source tree. The clean tree can be found
     at:

       src/third_party/yasm/source/yasm

  2) Run configure on the pristine source from a different directory (eg.,
     /tmp/yasm_build).  Running configure from another directory will keep
     the source tree clean.

  3) Next, capture all the output from a build of yasm.  We will use the build
     log as a reference for making the yasm.gyp file.

       make yasm > yasm_build_log 2> yasm_build_err

  4) Check yasm_build_err to see if there are any anomalies beyond yasm's
     compiler warnings.

  5) Grab the generated Makefile, libyasm-stdint.h, config.h, and put into
     the correct platform location. For android platform, copy the files
     generated for linux, but make sure that ENABLE_NLS is not defined to
     allow mac host compiles to work.  For ios, copy the files from mac.

       src/third_party/yasm/source/config/[platform]

     While we do not directly use the "Makefile" to build, it is needed by
     the "genmodule" subprogram as input for creating the available modules
     list.

  6) Make sure all the subprograms are represented in yasm.gyp.

       grep '^gcc' yasm_build_log  |
       grep -v ' -DHAVE_CONFIG_H '

     The yasm build creates a bunch of subprograms that in-turn generate
     more .c files in the build. Luckily the commands to generate the
     subprogram do not have -DHAVE_CONFIG_H as a cflag.

     From this list, make sure all the subprograms that are build have
     appropriate targets in the yasm.gyp.

     You will notice, when you get to the next step, that there are some
     .c source files that are compiled both for yasm, and for genperf.

     Those should go into the genperf_libs target so that they can be
     shared by the genperf and yasm targets.  Find those files by appending

       | grep 'gp-'

     to the command above.

  7) Find all the source files used to build yasm proper.

       grep -E '^gcc' yasm_build_log  |
       grep ' -DHAVE_CONFIG_H ' |
       awk '{print $NF }' |
       sed -e "s/'\.\/'\`//" |  # Removes some garbage from the build line.
       sort -u |
       sed -e "s/\(.*\)/'\1',/"  # Add quotes to each line.

     Reversing the -DHAVE_CONFIG_H filter from the command above should
     list the compile lines for yasm proper.

     This should get you close, but you will need to manually examine this
     list.  However, some of the built products are still included in the
     command above.  Generally, if the source file is in the root directory,
     it's a generated file.

     Inspect the current yasm.gyp for a list of the subprograms and their
     outputs.

     Update the sources list in the yasm target accordingly.  Read step #9
     as well if you update the source list to avoid problems.

  8) Update the actions for each of the subprograms.

     Here is the real fun.  For each subprogram created, you will need to
     update the actions and rules in yasm.gyp that invoke the subprogram to
     generate the files needed by the rest of the build.

     I don't have any good succinct instructions for this.  Grep the build
     log for each subprogram invocation (eg., "./genversion"), look at
     its command inputs and output, then verify our yasm.gyp does something
     similar.

     The good news is things likely only link or compile if this is done
     right so you'll know if there is a problem.

     Again, refer to the existing yasm.gyp for a guide to how the generated
     files are used.

     Here are a few gotchas:
       1) genmodule, by default, writes module.c into the current
          directory.  This does not play nicely with gyp.  We patch the
          source during build to allow specifying a specific output file.

       2) Most of the generated files, even though they are .c files, are
          #included by other files in the build.  Make sure they end up
          in a directory that is in the include path for the build.
          One of <(shared_generated_dir) or <(generated_dir) should work.

       3) Some of the genperf output is #included while others need to be
          compiled directly.  That is why there are 2 different rules for
          .gperf files in two targets.

  9) Check for python scripts that are run.

       grep python yasm_build_log

     Yasm uses python scripts to generate the assembly code description
     files in C++. Make sure to get these put into the gyp file properly as
     well.  An example is gen_x86_insn.py for x86 assembly.

     Note that at least the gen_x86_insn.py script suffers from the same
     problem as genmacro in that it outputs to the current directory by
     default.  The yasm.gyp build patches this file before invoking it to
     allow specifying an output directory.

 10) Recreate the 'AdditionalOptions!': [ '/analyze' ] block so that VC++
     /analyze builds won't fail.

 11) If all that's is finished, attempt to build....and cross your fingers.