Don't use -fPIC on Cygwin, either

Identify Cygwin-targetted gcc as sui generis (don't use -fPIC, but don't
link with standard Windows libraries, either)

Update tests appropriately

mesonbuild/compilers.py

@@ -2309,6 +2309,7 @@ class VisualStudioCPPCompiler(VisualStudioCCompiler, CPPCompiler):
 GCC_STANDARD = 0
 GCC_OSX = 1
 GCC_MINGW = 2
+GCC_CYGWIN = 3
 
 CLANG_STANDARD = 0
 CLANG_OSX = 1
@@ -2324,7 +2325,7 @@ def get_gcc_soname_args(gcc_type, prefix, shlib_name, suffix, path, soversion, i
         sostr = ''
     else:
         sostr = '.' + soversion
-    if gcc_type == GCC_STANDARD or gcc_type == GCC_MINGW:
+    if gcc_type in (GCC_STANDARD, GCC_MINGW, GCC_CYGWIN):
         # Might not be correct for mingw but seems to work.
         return ['-Wl,-soname,%s%s.%s%s' % (prefix, shlib_name, suffix, sostr)]
     elif gcc_type == GCC_OSX:
@@ -2398,7 +2399,7 @@ class GnuCompiler:
             return self.defines[define]
 
     def get_pic_args(self):
-        if self.gcc_type in (GCC_MINGW, GCC_OSX):
+        if self.gcc_type in (GCC_CYGWIN, GCC_MINGW, GCC_OSX):
             return [] # On Window and OS X, pic is always on.
         return ['-fPIC']
 
@@ -2796,7 +2797,7 @@ class FortranCompiler(Compiler):
         return ' '.join(self.exelist)
 
     def get_pic_args(self):
-        if self.gcc_type in (GCC_MINGW, GCC_OSX):
+        if self.gcc_type in (GCC_CYGWIN, GCC_MINGW, GCC_OSX):
             return [] # On Window and OS X, pic is always on.
         return ['-fPIC']
 

mesonbuild/environment.py

@@ -368,7 +368,8 @@ class Environment:
             return GCC_OSX
         elif '__MINGW32__' in defines or '__MINGW64__' in defines:
             return GCC_MINGW
-        # We ignore Cygwin for now, and treat it as a standard GCC
+        elif '__CYGWIN__' in defines:
+            return GCC_CYGWIN
         return GCC_STANDARD
 
     def _get_compilers(self, lang, evar, want_cross):

mesonbuild/mesonlib.py

@@ -212,6 +212,10 @@ def is_windows():
     platname = platform.system().lower()
     return platname == 'windows' or 'mingw' in platname
 
+def is_cygwin():
+    platname = platform.system().lower()
+    return platname.startswith('cygwin')
+
 def is_debianlike():
     return os.path.isfile('/etc/debian_version')
 

run_unittests.py

@@ -24,7 +24,7 @@ from pathlib import PurePath
 import mesonbuild.compilers
 import mesonbuild.environment
 import mesonbuild.mesonlib
-from mesonbuild.mesonlib import is_windows, is_osx
+from mesonbuild.mesonlib import is_windows, is_osx, is_cygwin
 from mesonbuild.environment import detect_ninja, Environment
 from mesonbuild.dependencies import PkgConfigDependency, ExternalProgram
 
@@ -833,6 +833,8 @@ class AllPlatformTests(BasePlatformTests):
                     self.assertEqual(cc.gcc_type, mesonbuild.compilers.GCC_OSX)
                 elif is_windows():
                     self.assertEqual(cc.gcc_type, mesonbuild.compilers.GCC_MINGW)
+                elif is_cygwin():
+                    self.assertEqual(cc.gcc_type, mesonbuild.compilers.GCC_CYGWIN)
                 else:
                     self.assertEqual(cc.gcc_type, mesonbuild.compilers.GCC_STANDARD)
             if isinstance(cc, clang):