deps: demote LLVM config to instance variable

Which fixes trying to use multiple versions of LLVM, and allows
simplifying the class somewhat.

mesonbuild/dependencies/dev.py

@@ -129,9 +129,6 @@ class LLVMDependency(ExternalDependency):
         'llvm-config-3.5', 'llvm-config35',
         'llvm-config-5.0', 'llvm-config-devel', # development snapshot
     ]
-    llvmconfig = None
-    _llvmconfig_found = False
-    __best_found = None
     __cpp_blacklist = {'-DNDEBUG'}
 
     def __init__(self, environment, kwargs):
@@ -139,11 +136,12 @@ class LLVMDependency(ExternalDependency):
         # the C linker works fine if only using the C API.
         super().__init__('llvm-config', environment, 'cpp', kwargs)
         self.modules = []
+        self.llvmconfig = None
+        self.__best_found = None
         # FIXME: Support multiple version requirements ala PkgConfigDependency
         req_version = kwargs.get('version', None)
-        if self.llvmconfig is None:
         self.check_llvmconfig(req_version)
-        if not self._llvmconfig_found:
+        if self.llvmconfig is None:
             if self.__best_found is not None:
                 mlog.log('found {!r} but need:'.format(self.__best_found),
                          req_version)
@@ -159,12 +157,14 @@ class LLVMDependency(ExternalDependency):
             mlog.debug('stdout: {}\nstderr: {}'.format(out, err))
             if self.required:
                 raise DependencyException('Dependency LLVM not found')
+            mlog.log('Dependency LLVM found:', mlog.red('NO'))
             return
-        else:
-            self.version = out.strip()
+
         mlog.log('Dependency LLVM found:', mlog.green('YES'))
         self.is_found = True
 
+        self.version = out.strip()
+
         p, out = Popen_safe(
             [self.llvmconfig, '--libs', '--ldflags', '--system-libs'])[:2]
         if p.returncode != 0:
@@ -193,38 +193,33 @@ class LLVMDependency(ExternalDependency):
             else:
                 mlog.log('LLVM module', mod, 'found:', mlog.green('YES'))
 
-    @classmethod
-    def check_llvmconfig(cls, version_req):
+    def check_llvmconfig(self, version_req):
         """Try to find the highest version of llvm-config."""
-        for llvmconfig in cls.llvm_config_bins:
+        for llvmconfig in self.llvm_config_bins:
             try:
                 p, out = Popen_safe([llvmconfig, '--version'])[0:2]
                 out = out.strip()
                 if p.returncode != 0:
                     continue
-                # FIXME: As soon as some llvm-config is found, version checks
-                # in further dependnecy() calls will be ignored
                 if version_req:
                     if version_compare(out, version_req, strict=True):
-                        if cls.__best_found and version_compare(out, '<={}'.format(cls.__best_found), strict=True):
+                        if self.__best_found and version_compare(
+                                out, '<={}'.format(self.__best_found), strict=True):
                             continue
-                        cls.__best_found = out
-                        cls.llvmconfig = llvmconfig
+                        self.__best_found = out
+                        self.llvmconfig = llvmconfig
                 else:
                     # If no specific version is requested use the first version
                     # found, since that should be the best.
-                    cls.__best_found = out
-                    cls.llvmconfig = llvmconfig
+                    self.__best_found = out
+                    self.llvmconfig = llvmconfig
                     break
             except (FileNotFoundError, PermissionError):
                 pass
-        if cls.__best_found:
+        if self.__best_found:
             mlog.log('Found llvm-config:',
-                     mlog.bold(shutil.which(cls.llvmconfig)),
+                     mlog.bold(shutil.which(self.llvmconfig)),
                      '({})'.format(out.strip()))
-            cls._llvmconfig_found = True
-        else:
-            cls.llvmconfig = False
 
     def need_threads(self):
         return True

test cases/frameworks/15 llvm/meson.build

@@ -10,8 +10,7 @@ llvm_dep = dependency(
 d = dependency('llvm', modules : 'not-found', required : false)
 assert(d.found() == false, 'not-found llvm module found')
 
-# XXX: Version checks are broken, see FIXME in LLVMDependency
-#d = dependency('llvm', version : '<0.1', required : false)
-#assert(d.found() == false, 'ancient llvm module found')
+d = dependency('llvm', version : '<0.1', required : false)
+assert(d.found() == false, 'ancient llvm module found')
 
 executable('sum', 'sum.c',  dependencies : llvm_dep)