I use KDevelop for plain C programming. When I change a function from:
static void
foo_bar (int a)
{
}

to:
static void
foo_baz (int a)
{
}

the auto-rename pops up offering to change all "foo_bar" calls to "foo_baz". 

But if I change it to:
static void
baz_foo_bar (int a)
{
}

It offers me to change it to 'az_foo_bar' (note the missing initial b). No matter what the new "prefix" is, it always omits the first letter of the new name in the suggestion.

Additionally, if I actually delete the first letter of the original function name the auto-rename stops reacting:
I start deleting the 'o' before the underscore in "foo_bar", it offers to replace "foo_bar" for "fo_bar". After deleting the second 'o', it offers "f_bar". If I delete the 'f', it keeps suggesting "f_bar" and stops reacting to any changes (like writing "baz"). If I write something *before* having deleted the 'f', the auto-rename works fine.

Reproducible: Always

Steps to Reproduce:
1. Write a funcion and use it in my code.
2. Rename the funcion affecting the first letter (either deleting it or adding a prefix).

Actual Results:  
3. Auto rename suggest wrong new name or none at all.

Expected Results:  
3. Auto rename suggest new function name as happens when first letter is untouched.