Overhaul versioning and naming of libraries

This commit contains several changes to the naming and versioning of
shared and static libraries. The details are documented at:
https://github.com/mesonbuild/meson/pull/417

Here's a brief summary:

* The results of binary and compiler detection via environment functions
  are now cached so that they can be called repeatedly without
  performance penalty. This is necessary because every
  build.SharedLibrary object has to know whether the compiler is MSVC or
  not (output filenames depend on that), and so the compiler detection
  has to be called for each object instantiation.

* Linux shared libraries don't always have a library version. Sometimes
  only soversions are specified (and vice-versa), so support both.

* Don't use versioned filenames when generating DLLs, DLLs are never
  versioned using the suffix in the way that .so libraries are. Hence,
  they don't use "aliases". Only Linux shared libraries use those.

* OS X dylibs do not use filename aliases at all. They only use the
  soversion in the dylib name (libfoo.X.dylib), and that's it. If
  there's no soversion specified, the dylib is called libfoo.dylib.
  Further versioning in dylibs is supposed to be done with the
  -current_version argument to clang, but this is TBD.

  https://developer.apple.com/library/mac/documentation/DeveloperTools/Conceptual/DynamicLibraries/100-Articles/DynamicLibraryDesignGuidelines.html#//apple_ref/doc/uid/TP40002013-SW23

* Install DLLs into bindir and import libraries into libdir

* Static libraries are now always called libfoo.a, even with MSVC

* .lib import libraries are always generated when building with MSVC

* .dll.a import libraries are always generated when building with
  MinGW/GCC or MinGW/clang

* TODO: Use dlltool if available to generate .dll.a when .lib is
  generated and vice-versa.

* Library and executable suffix/prefixes are now always correctly
  overriden by the values of the 'name_prefix' and 'name_suffix' keyword
  arguments.

1 files changed, 43 insertions, 44 deletions

diff --git a/mesonbuild/environment.py b/mesonbuild/environment.py
index e1e4613..f74b588 100644
--- a/mesonbuild/environment.py
+++ b/mesonbuild/environment.py
@@ -80,11 +80,37 @@ def detect_system():
     return platform.system().lower()
 
 
+def for_windows(is_cross, env):
+    """
+    Host machine is windows?
+
+    Note: 'host' is the machine on which compiled binaries will run
+    """
+    if not is_cross:
+        return mesonlib.is_windows()
+    elif env.cross_info.has_host():
+        return env.cross_info.config['host_machine']['system'] == 'windows'
+    return False
+
+def for_darwin(is_cross, env):
+    """
+    Host machine is Darwin (iOS/OS X)?
+
+    Note: 'host' is the machine on which compiled binaries will run
+    """
+    if not is_cross:
+        return mesonlib.is_osx()
+    elif env.cross_info.has_host():
+        return env.cross_info.config['host_machine']['system'] == 'darwin'
+    return False
+
+
 class Environment():
     private_dir = 'meson-private'
     log_dir = 'meson-logs'
     coredata_file = os.path.join(private_dir, 'coredata.dat')
     version_regex = '\d+(\.\d+)+(-[a-zA-Z0-9]+)?'
+
     def __init__(self, source_dir, build_dir, main_script_file, options, original_cmd_line_args):
         assert(os.path.isabs(main_script_file))
         assert(not os.path.islink(main_script_file))
@@ -122,33 +148,22 @@ class Environment():
         self.default_static_linker = 'ar'
         self.vs_static_linker = 'lib'
 
+        # Various prefixes and suffixes for import libraries, shared libraries,
+        # static libraries, and executables.
+        # Versioning is added to these names in the backends as-needed.
         cross = self.is_cross_build()
         if (not cross and mesonlib.is_windows()) \
         or (cross and self.cross_info.has_host() and self.cross_info.config['host_machine']['system'] == 'windows'):
             self.exe_suffix = 'exe'
-            if self.detect_c_compiler(cross).get_id() == 'msvc':
-                self.import_lib_suffix = 'lib'
-            else:
-                # MinGW-GCC doesn't generate and can't link with a .lib
-                # It uses the DLL file as the import library
-                self.import_lib_suffix = 'dll'
-            self.shared_lib_suffix = 'dll'
-            self.shared_lib_prefix = ''
-            self.static_lib_suffix = 'lib'
-            self.static_lib_prefix = ''
             self.object_suffix = 'obj'
+            self.shared_lib_dir = self.get_bindir()
         else:
             self.exe_suffix = ''
-            if (not cross and mesonlib.is_osx()) or \
-            (cross and self.cross_info.has_host() and self.cross_info.config['host_machine']['system'] == 'darwin'):
-                self.shared_lib_suffix = 'dylib'
-            else:
-                self.shared_lib_suffix = 'so'
-            self.shared_lib_prefix = 'lib'
-            self.static_lib_suffix = 'a'
-            self.static_lib_prefix = 'lib'
             self.object_suffix = 'o'
-            self.import_lib_suffix = self.shared_lib_suffix
+            self.shared_lib_dir = self.get_libdir()
+        # Common to all platforms
+        self.import_lib_dir = self.get_libdir()
+        self.static_lib_dir = self.get_libdir()
 
     def is_cross_build(self):
         return self.cross_info is not None
@@ -641,22 +656,17 @@ class Environment():
     def get_exe_suffix(self):
         return self.exe_suffix
 
-    # On Windows (MSVC) the library has suffix dll
-    # but you link against a file that has suffix lib.
-    def get_import_lib_suffix(self):
-        return self.import_lib_suffix
+    def get_import_lib_dir(self):
+        "Install dir for the import library (library used for linking)"
+        return self.import_lib_dir
 
-    def get_shared_lib_prefix(self):
-        return self.shared_lib_prefix
+    def get_shared_lib_dir(self):
+        "Install dir for the shared library"
+        return self.shared_lib_dir
 
-    def get_shared_lib_suffix(self):
-        return self.shared_lib_suffix
-
-    def get_static_lib_prefix(self):
-        return self.static_lib_prefix
-
-    def get_static_lib_suffix(self):
-        return self.static_lib_suffix
+    def get_static_lib_dir(self):
+        "Install dir for the static library"
+        return self.static_lib_dir
 
     def get_object_suffix(self):
         return self.object_suffix
@@ -682,17 +692,6 @@ class Environment():
     def get_datadir(self):
         return self.coredata.get_builtin_option('datadir')
 
-    def find_library(self, libname, dirs):
-        if dirs is None:
-            dirs = mesonlib.get_library_dirs()
-        suffixes = [self.get_shared_lib_suffix(), self.get_static_lib_suffix()]
-        prefix = self.get_shared_lib_prefix()
-        for d in dirs:
-            for suffix in suffixes:
-                trial = os.path.join(d, prefix + libname + '.' + suffix)
-                if os.path.isfile(trial):
-                    return trial
-
 
 def get_args_from_envvars(lang):
     if lang == 'c':