fix broken IR generation logic for globals

Author: varun-r-mallya

pythonbpf/globals_pass.py

@@ -34,11 +34,11 @@ def emit_global(module: ir.Module, node, name):
 
     # constructor call like "return c_int64(0)" or dataclass(...)
     elif isinstance(init_val, ast.Call):
-        if len(init_val.args) == 1 and isinstance(init_val.args[0], ast.Constant):
+        if len(init_val.args) >= 1 and isinstance(init_val.args[0], ast.Constant):
             llvm_init = ir.Constant(ty, init_val.args[0].value)
         else:
-            raise ValueError(f"Complex constructor not supported: {ast.dump(init_val)}")
-
+            logger.info("Defaulting to zero as no constant argument found")
+            llvm_init = ir.Constant(ty, 0)
     else:
         raise ValueError(f"Unsupported return expr {ast.dump(init_val)}")
 
@@ -49,7 +49,6 @@ def emit_global(module: ir.Module, node, name):
     gvar.global_constant = False
     return gvar
 
-
 def globals_processing(tree, module):
     """Process stuff decorated with @bpf and @bpfglobal except license and return the section name"""
     globals_sym_tab = []

tests/failing_tests/globals.py

@@ -18,6 +18,73 @@ def somevalue2() -> c_int64:
 def somevalue1() -> c_int32:
     return c_int32(0)
 
+import ast
+from dataclasses import dataclass
+from typing import List
+
+# --- Passing examples ---
+
+# Simple constant return
+@bpf
+@bpfglobal
+def g1() -> c_int64:
+    return 42
+
+# Constructor with one constant argument
+@bpf
+@bpfglobal
+def g2() -> c_int64:
+    return c_int64(0)
+
+
+# --- Failing examples ---
+
+# No return annotation
+# @bpf
+# @bpfglobal
+# def g3():
+#     return 42
+
+# Return annotation is complex
+# @bpf
+# @bpfglobal
+# def g4() -> List[int]:
+#     return []
+
+# # Return is missing
+# @bpf
+# @bpfglobal
+# def g5() -> c_int64:
+#     pass
+
+# # Return is a variable reference
+# #TODO: maybe fix this sometime later. It defaults to 0
+CONST = 5
+@bpf
+@bpfglobal
+def g6() -> c_int64:
+    return c_int64(CONST)
+
+# Constructor with multiple args
+#TODO: this is not working. should it work ?
+@bpf
+@bpfglobal
+def g7() -> c_int64:
+    return c_int64(1, 2)
+
+# Dataclass call
+#TODO: fails with dataclass
+# @dataclass
+# class Point:
+#     x: c_int64
+#     y: c_int64
+
+# @bpf
+# @bpfglobal
+# def g8() -> Point:
+#     return Point(1, 2)
+
+
 @bpf
 @section("tracepoint/syscalls/sys_enter_execve")
 def sometag(ctx: c_void_p) -> c_int64: