[MesonToolchain] Added extra_xxxxx flags (#16389)

Added extra_xxxxx flags

conan/tools/meson/toolchain.py

@@ -194,6 +194,17 @@ def __init__(self, conanfile, backend=None, native=False):
             if vscrt:
                 self._b_vscrt = str(vscrt).lower()
 
+        # Extra flags
+        #: List of extra CXX flags. Added to cpp_args
+        self.extra_cxxflags = []
+        #: List of extra C flags. Added to c_args
+        self.extra_cflags = []
+        #: List of extra linker flags. Added to c_link_args and cpp_link_args
+        self.extra_ldflags = []
+        #: List of extra preprocessor definitions. Added to c_args and cpp_args with the
+        #: format -DFLAG1
+        self.extra_defines = []
+
         #: Dict-like object that defines Meson``properties`` with ``key=value`` format
         self.properties = {}
         #: Dict-like object that defines Meson ``project options`` with ``key=value`` format
@@ -408,13 +419,14 @@ def _get_extra_flags(self):
         exelinkflags = self._conanfile_conf.get("tools.build:exelinkflags", default=[], check_type=list)
         linker_scripts = self._conanfile_conf.get("tools.build:linker_scripts", default=[], check_type=list)
         linker_script_flags = ['-T"' + linker_script + '"' for linker_script in linker_scripts]
-        defines = [f"-D{d}" for d in self._conanfile.conf.get("tools.build:defines", default=[], check_type=list)]
+        defines = self._conanfile.conf.get("tools.build:defines", default=[], check_type=list)
         sys_root = [f"--sysroot={self._sys_root}"] if self._sys_root else [""]
         return {
-            "cxxflags": cxxflags + sys_root,
-            "cflags": cflags + sys_root,
-            "ldflags": sharedlinkflags + exelinkflags + linker_script_flags + sys_root,
-            "defines": defines
+            "cxxflags": cxxflags + sys_root + self.extra_cxxflags,
+            "cflags": cflags + sys_root + self.extra_cflags,
+            "ldflags": sharedlinkflags + exelinkflags + linker_script_flags
+                       + sys_root + self.extra_ldflags,
+            "defines": [f"-D{d}" for d in (defines + self.extra_defines)]
         }
 
     @staticmethod

test/integration/toolchains/meson/test_mesontoolchain.py

@@ -105,6 +105,46 @@ def test_extra_flags_via_conf():
     assert "cpp_link_args = ['-flag0', '-other=val', '-flag5', '-flag6']" in content
 
 
+def test_extra_flags_via_toolchain():
+    profile = textwrap.dedent("""
+        [settings]
+        os=Windows
+        arch=x86_64
+        compiler=gcc
+        compiler.version=9
+        compiler.cppstd=17
+        compiler.libcxx=libstdc++
+        build_type=Release
+
+        [buildenv]
+        CFLAGS=-flag0 -other=val
+        CXXFLAGS=-flag0 -other=val
+        LDFLAGS=-flag0 -other=val
+   """)
+    t = TestClient()
+    conanfile = textwrap.dedent("""
+    from conan import ConanFile
+    from conan.tools.meson import MesonToolchain
+    class Pkg(ConanFile):
+        settings = "os", "compiler", "arch", "build_type"
+        def generate(self):
+            tc = MesonToolchain(self)
+            tc.extra_cxxflags = ["-flag1", "-flag2"]
+            tc.extra_cflags = ["-flag3", "-flag4"]
+            tc.extra_ldflags = ["-flag5", "-flag6"]
+            tc.extra_defines = ["define1=0"]
+            tc.generate()
+    """)
+    t.save({"conanfile.py": conanfile,
+            "profile": profile})
+    t.run("install . -pr:h=profile -pr:b=profile")
+    content = t.load(MesonToolchain.native_filename)
+    assert "cpp_args = ['-flag0', '-other=val', '-flag1', '-flag2', '-Ddefine1=0', '-D_GLIBCXX_USE_CXX11_ABI=0']" in content
+    assert "c_args = ['-flag0', '-other=val', '-flag3', '-flag4', '-Ddefine1=0']" in content
+    assert "c_link_args = ['-flag0', '-other=val', '-flag5', '-flag6']" in content
+    assert "cpp_link_args = ['-flag0', '-other=val', '-flag5', '-flag6']" in content
+
+
 def test_linker_scripts_via_conf():
     profile = textwrap.dedent("""
         [settings]