Merge pull request #564 from whoami730/exceptions

Parse and display exception table

Author: zrax

bytecode.cpp

@@ -600,3 +600,18 @@ void bc_disasm(std::ostream& pyc_output, PycRef<PycCode> code, PycModule* mod,
         pyc_output << "\n";
     }
 }
+
+void bc_exceptiontable(std::ostream& pyc_output, PycRef<PycCode> code,
+               int indent)
+{
+    for (const auto& entry : code->exceptionTableEntries()) {
+
+        for (int i=0; i<indent; i++)
+            pyc_output << "    ";
+
+        pyc_output << entry.start_offset << " to " << entry.end_offset
+                   << " -> " << entry.target << " [" << entry.stack_depth
+                   << "] " << (entry.push_lasti ? "lasti": "")
+                   << "\n";
+    }
+}

bytecode.h

@@ -32,3 +32,5 @@ void print_const(std::ostream& pyc_output, PycRef<PycObject> obj, PycModule* mod
 void bc_next(PycBuffer& source, PycModule* mod, int& opcode, int& operand, int& pos);
 void bc_disasm(std::ostream& pyc_output, PycRef<PycCode> code, PycModule* mod,
                int indent, unsigned flags);
+void bc_exceptiontable(std::ostream& pyc_output, PycRef<PycCode> code,
+               int indent);

pyc_code.cpp

@@ -128,3 +128,44 @@ PycRef<PycString> PycCode::getCellVar(PycModule* mod, int idx) const
         ? m_freeVars->get(idx - m_cellVars->size()).cast<PycString>()
         : m_cellVars->get(idx).cast<PycString>();
 }
+
+int _parse_varint(PycBuffer& data, int& pos) {
+    int b = data.getByte();
+    pos += 1;
+
+    int val = b & 0x3F;
+    while (b & 0x40) {
+        val <<= 6;
+
+        b = data.getByte();
+        pos += 1;
+
+        val |= (b & 0x3F);
+    }
+    return val;
+}
+
+std::vector<PycExceptionTableEntry> PycCode::exceptionTableEntries() const
+{
+    PycBuffer data(m_exceptTable->value(), m_exceptTable->length());
+
+    std::vector<PycExceptionTableEntry> entries;
+
+    int pos = 0;
+    while (!data.atEof()) {
+
+        int start = _parse_varint(data, pos) * 2;
+        int length = _parse_varint(data, pos) * 2;
+        int end = start + length;
+        
+        int target = _parse_varint(data, pos) * 2;
+        int dl = _parse_varint(data, pos);
+
+        int depth = dl >> 1;
+        bool lasti = bool(dl & 1);
+        
+        entries.push_back(PycExceptionTableEntry(start, end, target, depth, lasti));
+    }
+    
+    return entries;
+}

pyc_code.h

@@ -8,6 +8,18 @@
 class PycData;
 class PycModule;
 
+class PycExceptionTableEntry {
+public:
+    int start_offset; // inclusive
+    int end_offset; // exclusive
+    int target;
+    int stack_depth;
+    bool push_lasti;
+
+    PycExceptionTableEntry(int m_start_offset, int m_end_offset, int m_target, int m_stack_depth, bool m_push_lasti) :
+        start_offset(m_start_offset), end_offset(m_end_offset), target(m_target), stack_depth(m_stack_depth), push_lasti(m_push_lasti) {};
+};
+
 class PycCode : public PycObject {
 public:
     typedef std::vector<PycRef<PycString>> globals_t;
@@ -87,6 +99,8 @@ class PycCode : public PycObject {
         m_globalsUsed.emplace_back(std::move(varname));
     }
 
+    std::vector<PycExceptionTableEntry> exceptionTableEntries() const;
+
 private:
     int m_argCount, m_posOnlyArgCount, m_kwOnlyArgCount, m_numLocals;
     int m_stackSize, m_flags;

pycdas.cpp

@@ -154,16 +154,16 @@ void output_object(PycRef<PycObject> obj, PycModule* mod, int indent,
             iputs(pyc_output, indent + 1, "[Disassembly]\n");
             bc_disasm(pyc_output, codeObj, mod, indent + 2, flags);
 
+            if (mod->verCompare(3, 11) >= 0) {
+                iputs(pyc_output, indent + 1, "[Exception Table]\n");
+                bc_exceptiontable(pyc_output, codeObj, indent+2);
+            }
+
             if (mod->verCompare(1, 5) >= 0 && (flags & Pyc::DISASM_PYCODE_VERBOSE) != 0) {
                 iprintf(pyc_output, indent + 1, "First Line: %d\n", codeObj->firstLine());
                 iputs(pyc_output, indent + 1, "[Line Number Table]\n");
                 output_object(codeObj->lnTable().cast<PycObject>(), mod, indent + 2, flags, pyc_output);
             }
-
-            if (mod->verCompare(3, 11) >= 0 && (flags & Pyc::DISASM_PYCODE_VERBOSE) != 0) {
-                iputs(pyc_output, indent + 1, "[Exception Table]\n");
-                output_object(codeObj->exceptTable().cast<PycObject>(), mod, indent + 2, flags, pyc_output);
-            }
         }
         break;
     case PycObject::TYPE_STRING: