Ghidra: Detect typical for loops

[henke37]

The decompiler takes a rather pessimistic approach and considers all loops to be while loops. For patterns known to be traditionally written using for loops, it should output the loop as a for loop instead.

[Piruzzolo]

for instance,

void __thiscall SymbolTable(SymbolTable *this,int param_1)

{
  SymbolHashNode **ppSVar1;
  int iVar2;

  this->size = param_1;
  ppSVar1 = (SymbolHashNode **)
            operator_new__(-(uint)((int)((ulonglong)(uint)param_1 * 4 >> 0x20) != 0) |
                           (uint)((ulonglong)(uint)param_1 * 4));
  this->bucket = ppSVar1;
  iVar2 = 0;
  if (0 < this->size) {
    do {
      this->bucket[iVar2] = (SymbolHashNode *)0x0;
      iVar2 = iVar2 + 1;
    } while (iVar2 < this->size);
  }
  return;
}

may be converted to

void __thiscall SymbolTable::SymbolTable(SymbolTable *this, int param_1)
{
  SymbolTable *v2; 
  int i; 
  this->size = param_1;
  this->bucket = (SymbolHashNode **)operator new[](4 * param_1); // maybe too c++ish
  for ( i = 0; i < this->size; ++i )
    this->bucket[i] = 0;
}

it could also go further by noting that i's scope is the loop and write "int i = 0". Also note the rewrite of operator new's argument

[Piruzzolo]

@ryanmkurtz Any news for this issue? Are you devs working / planning to work on this?

[ryanmkurtz]

No news that I am aware of, but I'll check with the right people and get back to you.

[ryanmkurtz]

No one is working on it yet, but it's on the list of things to do. Unfortunately at this time I can't give you a prediction of when it will be started.

[Piruzzolo]

Thanks, good to know :+1:

[ccarpenter04]

I would also really like to see different types of loops be represented better by the decompiler. As you can see in the example provided by @Piruzzolo it would help clean up the code a lot, especially in larger, already complex functions.