[fpc-devel] estimating function code size

Ċ½ilvinas Ledas zilvinas.ledas at dict.lt
Wed Jan 18 14:17:38 CET 2012


On 2012-01-18 15:08, Gennadiy Poryev wrote:
>> Do you think it's granted that there is only one return in a function ?
>> Maybe optimization or "exit" could create additional returns
> Actually I do. Because I write this function :)
> It uses quite a lot of loops and ifs, but no exits.
> And what I need is a reliable way to get its code size at runtime without manually inspecting it on every rebuild.

I had similar problem a year and a half ago. I ended up looking for 
"ret" using disassembler.

Regarding one ret per function, I got this response from Jonas at that time:

On 2010-07-18 15:42, Jonas Maebe wrote:
> On 18 Jul 2010, at 13:14, Ċ½ilvinas Ledas wrote:
>
>> I want to use it this way:
>> 1) Gel all @unitname.function addresses.
>> 2) Use disassembler to find nearest next RET.
>> 3) Then I assume that I have start and end of the function in the binary file.
>>
>> It works at least for the concept-showing app with some functions and enabled optimizations when compiling. Do I have some conceptual flaw?
> Yes: there is no guarantee that a function will contain only one "ret" (it is that way currently for compiler-generated code, but that can change at any time).
>
>
> Jonas




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