Bug 1676896 - Remove pycparser dependencies from rnp_symbols.py to make it more accessible. r=kaie

The recently added RNP_API macro makes it much easier to find the necessary functions to export
with a simple regex.

Differential Revision: https://phabricator.services.mozilla.com/D96839

--HG--
extra : moz-landing-system : lando

python/thirdroc/thirdroc/rnp_symbols.py

@@ -5,56 +5,58 @@
 """
 Parse rnp/rnp.h header file and build a symbols file suitable
 for use with mozbuild.
+
+This script is meant to be run when the public C API of librnp adds or removes functions so that
+they can be exported by the shared library.
+
+Limitations: The regex that captures the function name is very basic and may need adjusting if
+the third_party/rnp/include/rnp/rnp.h format changes too much.
+Also note that APIs that are marked deprecated are not checked for.
+
+Dependencies: Only Python 3
+
+Running:
+  python3 rnp_symbols.py
+
+Output will be on stdout, this is to give the developer the opportunity to compare the old and
+new versions and check for accuracy.
 """
 
 from __future__ import absolute_import, print_function
 
 import sys
 import os
-
-try:
-    import pycparser_fake_libc
-    from pycparser import parse_file
-    from pycparser.c_ast import Decl
-    from pycparserext.ext_c_parser import (
-        FuncDeclExt,
-        GnuCParser,
-    )
-except ImportError:
-    print(
-        "One or more dependencies not found: pycparser, pycparserext, pycparser_fake_libc"
-    )
-    sys.exit(1)
+import re
 
 HERE = os.path.dirname(__file__)
 TOPSRCDIR = os.path.abspath(os.path.join(HERE, "../../../../"))
 RNPSRCDIR = os.path.join(TOPSRCDIR, "comm/third_party/rnp")
 
 
-def is_func(obj):
-    if isinstance(obj, Decl):
-        return isinstance(obj.type, FuncDeclExt)
+FUNC_DECL_RE = re.compile(r"^RNP_API\s+.*?([a-zA-Z0-9_]+)\(.*$")
+
+
+def get_func_name(line):
+    """
+    Extract the function name from a RNP_API function declaration.
+    Examples:
+    RNP_API rnp_result_t rnp_enable_debug(const char *file);
+
+    RNP_API rnp_result_t rnp_ffi_create(rnp_ffi_t * ffi,
+    """
+    m = FUNC_DECL_RE.match(line)
+    return m.group(1)
 
 
 def extract_func_defs(filename):
-    # Note that cpp is used. Provide a path to your own cpp or
-    # make sure one exists in PATH.
-    rnp_export_path = os.path.join(RNPSRCDIR, "src/lib")
-    ast = parse_file(
-        filename,
-        use_cpp=True,
-        cpp_args=[
-            "-E",
-            "-I{}".format(rnp_export_path),
-            "-I{}".format(pycparser_fake_libc.directory),
-        ],
-        parser=GnuCParser(lex_optimize=False, yacc_optimize=False),
-    )
-
-    for node in ast.children():
-        decl = node[1]
-        if is_func(decl):
-            yield decl.name
+    """
+    Look for RNP_API in the header file to find the names of the symbols that should be exported
+    """
+    with open(filename) as fp:
+        for line in fp:
+            if line.startswith("RNP_API"):
+                func_name = get_func_name(line)
+                yield func_name
 
 
 if __name__ == "__main__":
@@ -63,5 +65,5 @@ if __name__ == "__main__":
     else:
         FILENAME = os.path.join(RNPSRCDIR, "include/rnp/rnp.h")
 
-    for f in sorted(extract_func_defs(FILENAME)):
+    for f in sorted(list(extract_func_defs(FILENAME))):
         print(f)