Reducing Executable Size - Comment out calls/usage vs Remove files/folders

Question

My goal is to reduce the binary size of an existing Visual Studio 2013 C++ project.

As I understood from my previous semi-related question, the Linker will include pieces of code, in the binary file, only if the code is used.

As part of my attempts to identify which components (classes/folders/filters) in my projects are the largest, I tried the following:

Comment out calls/usage of these components.
1 + completely remove these components (files/folder) from my project.

I expected 2 to give the same results as 1 in terms of binary size. However found out that using 2 as much more impact on the size, meaning size reduction is much better.

Questions

Is my assumption valid (2 to give the same results as 1)?
If so, why don't I get the expected results?

Update 1

It seems like the Linker still includes code of unused functions, as if its logic tells it that it cannot exclude these functions since they might be used somehow (for example: exported functions) Just a reminder, the functions/classes I wish to exclude are not exported.

Example 1

void func(HINSTANCE, LPVOID lpReserved)
{
   // do nothing
}

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpReserved)
{
   // do nothing
}

generates DLL of size ~300KB

Example 2

void func(HINSTANCE, LPVOID lpReserved)
{
   // do something huge
}

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpReserved)
{
   // do nothing
}

generated DLL of size ~400KB

Question:

When generating DLL, if function is not used/called and it is not exported, why would the linker include its code?

I configured my Linker flags based on Do unused functions get optimized out?

@Yakk Compiling in Release and Optimization flags favor size over speed. This is more a question on which code the linker includes in DLL and why then a question of how to resolve my issue. — idanshmu, Feb 18 '15 at 12:48
I'm sure providing the **all** information is more useful, but for the sake of the question, should I be concern with specific flags? — idanshmu, Feb 18 '15 at 12:54
By the size of the binary, do you mean the size of the `.exe` file, or the size of the process image in memory? — James Kanze, Feb 18 '15 at 12:57
If `func` is not used, I think it should be static or placed in anonymous namespace. When it is not, compiler can assume that the function can be required by another source file. — Piotr Siupa, Feb 18 '15 at 14:23
As a last resort you can compress `.dll` file using a program such as `UPX`. — Piotr Siupa, Feb 18 '15 at 14:32

Reducing Executable Size - Comment out calls/usage vs Remove files/folders

Questions

Update 1

Question:

0 Answers0