Redundant attachment of indirect object pronouns to infinitives

Question

edit: It seems I wrote my examples wrong. I wanted to write:

Quiero comermelo (I want to eat it)

Quiero comerlo (I want to eat it)

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I sometimes see that indirect object pronouns are attached to infinitives when there seems to be no reason to do so. For example compare:

Quieres comermelo. 
Quieres comerlo. 

As far as I know, these sentences mean the same (I want to eat it.)

So my question is, are there any semantic differences between these two? Or is this just an example of clitic doubling as in the sentence

Le di un regalo a mi madre 

Answer 1

Actually the pronouns make important distinctions in the example you provided and are not redundant:

Quieres comer.

Means, "You want to eat"

Quieres comerlo.

Means "You want to eat it", with "it" being that thing that has previously been named and the pronoun "lo" stands for.

Quieres comer? Hay un yogur en la nevera _{Do you want to eat? There is a yogurt in the fridge}

Hay un yogurt en la nevera. Quieres comerlo? _{There is a yogurt in the fridge. Do you want to eat it?}

Me he comprado un coche nuevo. Quieres probarlo? _{I got a new car. Do you want to test-drive it?}

It is the same for "comer-me-lo" or "comer-te-lo"

Hay un yogurt en la nevera. Quieres comértelo There is a yogurt in the fridge. Do you want to eat it?

The "te" is the reflexive pronoun for "you". The reflexive pronoun indicates who is the beneficiary of the action. Reflexives can be tricky to master. You can say "comértelo" to express that you receive the benefit of eating the yogurt, but you wouldn't do so with "probarlo" for the car, but you could do so with "probártelo with something like a suit or jeans

Quieres probarte esos pantalones vaqueros?

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Edit to address the latest comment.

You can write/say something like "Quiero comértelo". Imagine that you are playing with your 4 year old nephew. He is in your lap, you are tickling him and then you say "Now I'm going to eat your ears! I want to eat them!"

Voy a comerme tus orejas. Me las quiero comer

There you stress that you are going to eat the ears

Voy a comerte las orejas. Te las quiero comer

There you stress that his ears are going to be eaten, by you. If it is difficult to understand, think of it with the verb "morder".

Me muerdo las uñas / Tengo el hábito de morderme las uñas (You do the action to yourself)

Te muerdo la oreja (You do the action, somebody else receives the "benefit" of the action)

And if you change "la oreja" for a pronoun:

Quiero comérmela / Quiero comértela

So "Quiero comertelo" means that you are going to eat some body part of someone (because they will receive the action). You wouldn't say "quiero comértelo" for someone else's food, since even if the food belongs to them, they are not receiving the action of being eaten.

Answer 2

The indirect object pronouns used in your examples... Comérmelo, Comértelo...

Those pronouns, when used with comer, indicate eating all of something. To eat it all up. To lavish all of it. To engorge it all, consume it all.

So if you asked someone `¿Quieres comértelo?, you would literally be asking if that person wants to eat all of something.