[libc] Make hdrgen support macro_header YAML field. (#123265)

A macro can specify macro_header instead of macro_value to
indicate that an llvm-libc-macros/ header file is supposed to
define this macro.  This is used for dlfcn.h, which previously
bogusly redefined the RTLD_* macros to empty.

libc/include/dlfcn.yaml

@@ -2,13 +2,13 @@ header: dlfcn.h
 header_template: dlfcn.h.def
 macros:
   - macro_name: RTLD_LAZY
-    macro_value: null
+    macro_header: dlfcn-macros.h
   - macro_name: RTLD_NOW
-    macro_value: null
+    macro_header: dlfcn-macros.h
   - macro_name: RTLD_GLOBAL
-    macro_value: null
+    macro_header: dlfcn-macros.h
   - macro_name: RTLD_LOCAL
-    macro_value: null
+    macro_header: dlfcn-macros.h
 types: []
 enums: []
 objects: []

libc/utils/hdrgen/gpu_headers.py

@@ -8,6 +8,7 @@
 
 from header import HeaderFile
 
+
 class GpuHeaderFile(HeaderFile):
     def __str__(self):
         content = []

libc/utils/hdrgen/header.py

@@ -6,6 +6,8 @@
 #
 # ==-------------------------------------------------------------------------==#
 
+from pathlib import PurePath
+
 
 class HeaderFile:
     def __init__(self, name):
@@ -32,11 +34,26 @@ class HeaderFile:
     def add_function(self, function):
         self.functions.append(function)
 
+    def includes(self):
+        return sorted(
+            {
+                PurePath("llvm-libc-macros") / macro.header
+                for macro in self.macros
+                if macro.header is not None
+            }
+        )
+
     def public_api(self):
-        content = [""]
+        header_dir = PurePath(self.name).parent
+        content = [
+            f'#include "{file.relative_to(header_dir)}"' for file in self.includes()
+        ] + [""]
 
         for macro in self.macros:
-            content.append(f"{macro}\n")
+            # When there is nothing to define, the Macro object converts to str
+            # as an empty string.  Don't emit a blank line for those cases.
+            if str(macro):
+                content.append(f"{macro}\n")
 
         for type_ in self.types:
             content.append(f"{type_}")
@@ -76,11 +93,9 @@ class HeaderFile:
             content.append(f"#endif // {current_guard}")
             content.append("")
 
-        for object in self.objects:
-            content.append(str(object))
+        content.extend(str(object) for object in self.objects)
         if self.objects:
-            content.append("\n__END_C_DECLS")
-        else:
-            content.append("__END_C_DECLS")
+            content.append("")
+        content.append("__END_C_DECLS")
 
         return "\n".join(content)

libc/utils/hdrgen/macro.py

@@ -8,12 +8,14 @@
 
 
 class Macro:
-    def __init__(self, name, value=None):
+    def __init__(self, name, value=None, header=None):
         self.name = name
         self.value = value
+        self.header = header
 
     def __str__(self):
+        if self.header != None:
+            return ""
         if self.value != None:
             return f"#define {self.name} {self.value}"
-        else:
-            return f"#define {self.name}"
+        return f"#define {self.name}"

libc/utils/hdrgen/tests/expected_output/test_header.h

@@ -11,13 +11,17 @@
 
 #include "__llvm-libc-common.h"
 #include "llvm-libc-macros/float16-macros.h"
-#include "llvm-libc-macros/test_small-macros.h"
 #include "llvm-libc-types/float128.h"
 
+#include "llvm-libc-macros/test_more-macros.h"
+#include "llvm-libc-macros/test_small-macros.h"
+
 #define MACRO_A 1
 
 #define MACRO_B 2
 
+#define MACRO_C
+
 #include <llvm-libc-types/type_a.h>
 #include <llvm-libc-types/type_b.h>
 

libc/utils/hdrgen/tests/input/test_small.h.def

@@ -11,7 +11,6 @@
 
 #include "__llvm-libc-common.h"
 #include "llvm-libc-macros/float16-macros.h"
-#include "llvm-libc-macros/test_small-macros.h"
 #include "llvm-libc-types/float128.h"
 
 %%public_api()

libc/utils/hdrgen/tests/input/test_small.yaml

@@ -5,6 +5,11 @@ macros:
     macro_value: 1
   - macro_name: MACRO_B
     macro_value: 2
+  - macro_name: MACRO_C
+  - macro_name: MACRO_D
+    macro_header: test_small-macros.h
+  - macro_name: MACRO_E
+    macro_header: test_more-macros.h
 types:
   - type_name: type_a
   - type_name: type_b

libc/utils/hdrgen/tests/test_integration.py

@@ -10,6 +10,7 @@ class TestHeaderGenIntegration(unittest.TestCase):
         self.output_dir = TestHeaderGenIntegration.output_dir
         self.source_dir = Path(__file__).parent
         self.main_script = self.source_dir.parent / "main.py"
+        self.maxDiff = 80 * 100
 
     def run_script(self, yaml_file, output_file, entry_points):
         command = [

libc/utils/hdrgen/yaml_to_classes.py

@@ -38,7 +38,13 @@ def yaml_to_classes(yaml_data, header_class, entry_points=None):
     header.template_file = yaml_data.get("header_template")
 
     for macro_data in yaml_data.get("macros", []):
-        header.add_macro(Macro(macro_data["macro_name"], macro_data["macro_value"]))
+        header.add_macro(
+            Macro(
+                macro_data["macro_name"],
+                macro_data.get("macro_value"),
+                macro_data.get("macro_header"),
+            )
+        )
 
     types = yaml_data.get("types", [])
     sorted_types = sorted(types, key=lambda x: x["type_name"])