Merge pull request #3831 from mesonbuild/symvisibility

Add gnu_symbol_visibility keyword argument

docs/markdown/Reference-manual.md

@@ -511,6 +511,13 @@ be passed to [shared and static libraries](#library).
 - `override_options` takes an array of strings in the same format as
   `project`'s `default_options` overriding the values of these options
   for this target only, since 0.40.0
+- `gnu_symbol_visibility` specifies how symbols should be exported, see
+  e.g [the GCC Wiki](https://gcc.gnu.org/wiki/Visibility) for more
+  information. This value can either be an empty string or one of
+  `default`, `internal`, `hidden`, `protected` or `inlineshidden`, which
+  is the same as `hidden` but also includes things like C++ implicit
+  constructors as specified in the GCC manual. Ignored on compilers that
+  do not support GNU visibility arguments. Available since 0.48.0.
 - `d_import_dirs` list of directories to look in for string imports used
   in the D programming language
 - `d_unittest`, when set to true, the D modules are compiled in debug mode
@@ -976,15 +983,16 @@ dropped. That means that `join_paths('foo', '/bar')` returns `/bar`.
     buildtarget library(library_name, list_of_sources, ...)
 ```
 
-Builds a library that is either static, shared or both depending on the value of
-`default_library` user option. You should use this instead of
-[`shared_library`](#shared_library),
+Builds a library that is either static, shared or both depending on
+the value of `default_library` user option. You should use this
+instead of [`shared_library`](#shared_library),
 [`static_library`](#static_library) or
 [`both_libraries`](#both_libraries) most of the time. This allows you
 to toggle your entire project (including subprojects) from shared to
 static with only one option.
 
-The keyword arguments for this are the same as for [`executable`](#executable) with the following additions:
+The keyword arguments for this are the same as for
+[`executable`](#executable) with the following additions:
 
 - `name_prefix` the string that will be used as the prefix for the
   target output filename by overriding the default (only used for

docs/markdown/snippets/visibility.md

@@ -0,0 +1,13 @@
+## Keyword argument for GNU symbol visibility
+
+Build targets got a new keyword, `symbol_visibility` that controls how
+symbols are exported from shared libraries. This is most commonly used
+to hide implementation symbols like this:
+
+```meson
+shared_library('mylib', ...
+  gnu_symbol_visibility: 'hidden')
+```
+
+In this case only symbols explicitly marked as visible in the source
+files get exported.

mesonbuild/backend/ninjabackend.py

@@ -1951,6 +1951,8 @@ rule FORTRAN_DEP_HACK%s
         # Create an empty commands list, and start adding arguments from
         # various sources in the order in which they must override each other
         commands = CompilerArgs(compiler)
+        # Start with symbol visibility.
+        commands += compiler.gnu_symbol_visibility_args(target.gnu_symbol_visibility)
         # Add compiler args for compiling this target derived from 'base' build
         # options passed on the command-line, in default_options, etc.
         # These have the lowest priority.

mesonbuild/build.py

@@ -71,6 +71,7 @@ buildtarget_kwargs = set([
     'objects',
     'override_options',
     'sources',
+    'gnu_symbol_visibility',
 ])
 
 known_build_target_kwargs = (
@@ -817,6 +818,14 @@ This will become a hard error in a future Meson release.''')
         self.implicit_include_directories = kwargs.get('implicit_include_directories', True)
         if not isinstance(self.implicit_include_directories, bool):
             raise InvalidArguments('Implicit_include_directories must be a boolean.')
+        self.gnu_symbol_visibility = kwargs.get('gnu_symbol_visibility', '')
+        if not isinstance(self.gnu_symbol_visibility, str):
+            raise InvalidArguments('GNU symbol visibility must be a string.')
+        if self.gnu_symbol_visibility != '':
+            permitted = ['default', 'internal', 'hidden', 'protected', 'inlineshidden']
+            if self.gnu_symbol_visibility not in permitted:
+                raise InvalidArguments('GNU symbol visibility arg %s not one of: %s',
+                                       self.symbol_visibility, ', '.join(permitted))
 
     def get_filename(self):
         return self.filename

mesonbuild/compilers/compilers.py

@@ -311,6 +311,14 @@ vs64_instruction_set_args = {'mmx': ['/arch:AVX'],
                              'neon': None,
                              }
 
+gnu_symbol_visibility_args = {'': [],
+                              'default': ['-fvisibility=default'],
+                              'internal': ['-fvisibility=internal'],
+                              'hidden': ['-fvisibility=hidden'],
+                              'protected': ['-fvisibility=protected'],
+                              'inlineshidden': ['-fvisibility=hidden', '-fvisibility-inlines-hidden'],
+                              }
+
 def sanitizer_compile_args(value):
     if value == 'none':
         return []
@@ -1065,6 +1073,9 @@ class Compiler:
         # building fails with undefined symbols.
         return []
 
+    def gnu_symbol_visibility_args(self, vistype):
+        return []
+
 GCC_STANDARD = 0
 GCC_OSX = 1
 GCC_MINGW = 2
@@ -1280,6 +1291,8 @@ class GnuCompiler:
     def openmp_flags(self):
         return ['-fopenmp']
 
+    def gnu_symbol_visibility_args(self, vistype):
+        return gnu_symbol_visibility_args[vistype]
 
 class ElbrusCompiler(GnuCompiler):
     # Elbrus compiler is nearly like GCC, but does not support
@@ -1422,6 +1435,8 @@ class ClangCompiler:
             # Shouldn't work, but it'll be checked explicitly in the OpenMP dependency.
             return []
 
+    def gnu_symbol_visibility_args(self, vistype):
+        return gnu_symbol_visibility_args[vistype]
 
 class ArmclangCompiler:
     def __init__(self):

mesonbuild/interpreter.py

@@ -3854,6 +3854,7 @@ Try setting b_lundef to false instead.''')
         @FeatureNewKwargs('build target', '0.42.0', ['rust_crate_type', 'build_rpath', 'implicit_include_directories'])
         @FeatureNewKwargs('build target', '0.41.0', ['rust_args'])
         @FeatureNewKwargs('build target', '0.40.0', ['build_by_default'])
+        @FeatureNewKwargs('build target', '0.48.0', ['gnu_symbol_visibility'])
         def build_target_decorator_caller(self, node, args, kwargs):
             return True
 

mesonbuild/minit.py

@@ -72,16 +72,10 @@ lib_c_meson_template = '''project('{project_name}', 'c',
 # not the executables that use the library.
 lib_args = ['-DBUILDING_{utoken}']
 
-# Hiding symbols that are not explicitly marked as exported
-# requires a compiler flag on all compilers except VS.
-cc = meson.get_compiler('c')
-if cc.get_id() != 'msvc'
-  lib_args += ['-fvisibility=hidden']
-endif
-
 shlib = shared_library('{lib_name}', '{source_file}',
   install : true,
   c_args : lib_args,
+  gnu_symbol_visibility : 'hidden',
 )
 
 test_exe = executable('{test_exe_name}', '{test_source_file}',
@@ -226,16 +220,10 @@ lib_cpp_meson_template = '''project('{project_name}', 'cpp',
 # not the executables that use the library.
 lib_args = ['-DBUILDING_{utoken}']
 
-# Hiding symbols that are not explicitly marked as exported
-# requires a compiler flag on all compilers except VS.
-cpp = meson.get_compiler('cpp')
-if cpp.get_id() != 'msvc'
-  lib_args += ['-fvisibility=hidden']
-endif
-
 shlib = shared_library('{lib_name}', '{source_file}',
   install : true,
   cpp_args : lib_args,
+  gnu_symbol_visibility : 'hidden',
 )
 
 test_exe = executable('{test_exe_name}', '{test_source_file}',

test cases/failing build/2 hidden symbol/bob.c

@@ -0,0 +1,5 @@
+#include"bob.h"
+
+int hidden_function() {
+    return 7;
+}

test cases/failing build/2 hidden symbol/bob.h

@@ -0,0 +1,3 @@
+#pragma once
+
+int hidden_function();

test cases/failing build/2 hidden symbol/bobuser.c

@@ -0,0 +1,5 @@
+#include"bob.h"
+
+int main(int argc, char **argv) {
+    return hidden_function();
+}

test cases/failing build/2 hidden symbol/meson.build

@@ -0,0 +1,14 @@
+project('hidden symbol', 'c')
+
+if host_machine.system() == 'windows' or host_machine.system() == 'cygwin'
+  cc = meson.get_compiler('c')
+  if cc.get_id() == 'gcc'
+    error('MESON_SKIP_TEST -fvisibility=hidden does not work on MinGW or Cygwin.')
+  endif
+endif
+
+l = shared_library('bob', 'bob.c',
+  gnu_symbol_visibility: 'hidden')
+
+executable('bobuser', 'bobuser.c',
+  link_with: l)