find_library: Add a cache for library searchingnirbheek/find_library_fixes

Otherwise we can end up searching for the same library tens of times,
because pkg-config does not de-duplicate -lfoo args before returning
them.

We use -Wl,--start-group/end-group, so we do not need to worry about
ordering issues in static libraries.

4 files changed, 17 insertions, 10 deletions

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 354124ab2..4208b8985 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -46,6 +46,7 @@ from .compilers import (
 class CCompiler(Compiler):
     library_dirs_cache = {}
     program_dirs_cache = {}
+    find_library_cache = {}
 
     def __init__(self, exelist, version, is_cross, exe_wrapper=None, **kwargs):
         # If a child ObjC or CPP class has already set it, don't set it ourselves
@@ -837,13 +838,8 @@ class CCompiler(Compiler):
             raise AssertionError('BUG: unknown libtype {!r}'.format(libtype))
         return prefixes, suffixes
 
-    def find_library_impl(self, libname, env, extra_dirs, code, libtype='default'):
-        # These libraries are either built-in or invalid
-        if libname in self.ignore_libs:
-            return []
+    def find_library_real(self, libname, env, extra_dirs, code, libtype):
         # First try if we can just add the library as -l.
-        if extra_dirs and isinstance(extra_dirs, str):
-            extra_dirs = [extra_dirs]
         # Gcc + co seem to prefer builtin lib dirs to -L dirs.
         # Only try to find std libs if no extra dirs specified.
         if not extra_dirs and libtype == 'default':
@@ -864,7 +860,18 @@ class CCompiler(Compiler):
                     trial = os.path.join(d, prefix + libname + '.' + suffix)
                     if os.path.isfile(trial):
                         return [trial]
-        return None
+        return []
+
+    def find_library_impl(self, libname, env, extra_dirs, code, libtype):
+        # These libraries are either built-in or invalid
+        if libname in self.ignore_libs:
+            return []
+        if isinstance(extra_dirs, str):
+            extra_dirs = [extra_dirs]
+        key = (tuple(self.exelist), libname, tuple(extra_dirs), code, libtype)
+        if key not in self.find_library_cache:
+            self.find_library_cache[key] = self.find_library_real(libname, env, extra_dirs, code, libtype)
+        return self.find_library_cache[key][:]
 
     def find_library(self, libname, env, extra_dirs, libtype='default'):
         code = 'int main(int argc, char **argv) { return 0; }'
diff --git a/mesonbuild/compilers/vala.py b/mesonbuild/compilers/vala.py
index 6194d1aed..e89bc8db4 100644
--- a/mesonbuild/compilers/vala.py
+++ b/mesonbuild/compilers/vala.py
@@ -93,7 +93,7 @@ class ValaCompiler(Compiler):
             if os.path.isfile(vapi):
                 return [vapi]
         mlog.debug('Searched {!r} and {!r} wasn\'t found'.format(extra_dirs, libname))
-        return None
+        return []
 
     def thread_flags(self, env):
         return []
diff --git a/mesonbuild/dependencies/boost.py b/mesonbuild/dependencies/boost.py
index a17fb58de..301d7588e 100644
--- a/mesonbuild/dependencies/boost.py
+++ b/mesonbuild/dependencies/boost.py
@@ -363,7 +363,7 @@ class BoostDependency(ExternalDependency):
             libname = 'boost_' + module + tag
 
             args = self.compiler.find_library(libname, self.env, self.extra_lib_dirs())
-            if args is None:
+            if not args:
                 mlog.debug("Couldn\'t find library '{}' for boost module '{}'  (ABI tag = '{}')".format(libname, module, tag))
                 all_found = False
             else:
diff --git a/mesonbuild/dependencies/ui.py b/mesonbuild/dependencies/ui.py
index b07b0ae9f..4f4fe7852 100644
--- a/mesonbuild/dependencies/ui.py
+++ b/mesonbuild/dependencies/ui.py
@@ -568,7 +568,7 @@ class VulkanDependency(ExternalDependency):
             else:
                 # simply try to guess it, usually works on linux
                 libs = self.compiler.find_library('vulkan', environment, [])
-                if libs is not None and self.compiler.has_header('vulkan/vulkan.h', '', environment):
+                if libs and self.compiler.has_header('vulkan/vulkan.h', '', environment):
                     self.type_name = 'system'
                     self.is_found = True
                     self.version = 1 # TODO