[build] Use sysroot for linux compilation with clang

gypfiles/standalone.gypi

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 45 matching lines @@
               # Anything else gets passed through, which probably won't work
               # very well; such hosts should pass an explicit target_arch
               # to gyp.
               'host_arch%': '<!pymod_do_main(detect_v8_host_arch)',
             }, {
               # OS!="linux" and OS!="freebsd" and OS!="openbsd" and
               # OS!="netbsd" and OS!="mac" and OS!="aix"
               'host_arch%': 'ia32',
             }],
           ],
+
+          # By default we build against a stable sysroot image to avoid
+          # depending on the packages installed on the local machine. Set this
+          # to 0 to build against locally installed headers and libraries (e.g.
+          # if packaging for a linux distro)
+          'use_sysroot%': 1,
         },
         'host_arch%': '<(host_arch)',
         'target_arch%': '<(host_arch)',
+        'use_sysroot%': '<(use_sysroot)',
         'base_dir%': '<!(cd <(DEPTH) && python -c "import os; print os.getcwd()")',
 
         # Instrument for code coverage and use coverage wrapper to exclude some
         # files. Uses gcov if clang=0 is set explicitly. Otherwise,
         # sanitizer_coverage must be set too.
         'coverage%': 0,
+
+        'conditions': [
+          # The system root for linux builds.
+          ['OS=="linux" and use_sysroot==1', {
+            'conditions': [
+              ['target_arch=="arm"', {
+                'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_arm-sysroot',
+              }],
+              ['target_arch=="x64"', {
+                'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_amd64-sysroot',
+              }],
+              ['target_arch=="ia32"', {
+                'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_i386-sysroot',
+              }],
+              ['target_arch=="mipsel"', {
+                'sysroot%': '<!(cd <(DEPTH) && pwd -P)/build/linux/debian_wheezy_mips-sysroot',
+              }],
+            ],

[vogelheim, 2016/06/01 10:51:19]

I'm not sure what gyp does if OS is linux, use_sysroot is 1, but the target_arch
is different from those 4.

(Not sure this is worth fixing. The gyp conditional syntax is kind of horrible,
really.)

[Michael Achenbach, 2016/06/01 11:20:37]

I think it'll error out. So one should not set use_sysroot=1 in that case. An
if-else-if structure for the conditions above gets horribly nested in gyp. Or we
could provide a default on some structure level, but I think it's not worth it
as we can just set use_sysroot=0

+          }, {
+            'sysroot%': ''
+          }], # OS=="linux" and use_sysroot==1
+        ],
       },
       'base_dir%': '<(base_dir)',
       'host_arch%': '<(host_arch)',
       'target_arch%': '<(target_arch)',
       'v8_target_arch%': '<(target_arch)',
       'coverage%': '<(coverage)',
+      'sysroot%': '<(sysroot)',
       'asan%': 0,
       'lsan%': 0,
       'msan%': 0,
       'tsan%': 0,
       # Enable coverage gathering instrumentation in sanitizer tools. This flag
       # also controls coverage granularity (1 for function-level, 2 for
       # block-level, 3 for edge-level).
       'sanitizer_coverage%': 0,
       # Use libc++ (buildtools/third_party/libc++ and
       # buildtools/third_party/libc++abi) instead of stdlibc++ as standard
@@ skipping 67 matching lines @@
     'use_custom_libcxx%': '<(use_custom_libcxx)',
     'linux_use_bundled_gold%': '<(linux_use_bundled_gold)',
     'use_lto%': '<(use_lto)',
     'cfi_vptr%': '<(cfi_vptr)',
     'cfi_diag%': '<(cfi_diag)',
     'cfi_blacklist%': '<(cfi_blacklist)',
     'test_isolation_mode%': '<(test_isolation_mode)',
     'fastbuild%': '<(fastbuild)',
     'coverage%': '<(coverage)',
     'has_valgrind%': '<(has_valgrind)',
+    'sysroot%': '<(sysroot)',
 
     # Add a simple extras solely for the purpose of the cctests
     'v8_extra_library_files': ['../test/cctest/test-extra.js'],
     'v8_experimental_extra_library_files': ['../test/cctest/test-experimental-extra.js'],
 
     # .gyp files or targets should set v8_code to 1 if they build V8 specific
     # code, as opposed to external code.  This variable is used to control such
     # things as the set of warnings to enable, and whether warnings are treated
     # as errors.
     'v8_code%': 0,
@@ skipping 446 matching lines @@
             #
             # Disabled when using GCC LTO because GCC also uses the -B search
             # path at link time to find "as", and our bundled "as" can only
             # target x86.
             'ldflags': [
               # Note, Chromium allows ia32 host arch as well, we limit this to
               # x64 in v8.
               '-B<(base_dir)/third_party/binutils/Linux_x64/Release/bin',
             ],
           }],
+          ['sysroot!="" and clang==1', {
+            'target_conditions': [
+              ['_toolset=="target"', {
+                'cflags': [
+                  '--sysroot=<(sysroot)',
+                ],
+                'ldflags': [
+                  '--sysroot=<(sysroot)',
+                  '<!(<(DEPTH)/build/linux/sysroot_ld_path.sh <(sysroot))',
+                ],
+              }]]
+          }],
         ],
       },
     }],
     ['OS=="mac"', {
       'target_defaults': {
        'conditions': [
           ['asan==1', {
             'xcode_settings': {
               # FIXME(machenbach): This is outdated compared to common.gypi.
               'OTHER_CFLAGS+': [
@@ skipping 783 matching lines @@
               '-fsanitize=cfi-vcall',
               '-fsanitize=cfi-derived-cast',
               '-fsanitize=cfi-unrelated-cast',
             ],
           }],
         ],
       },
     }],
   ],
 }