How to implement two fluid columns, one of which depends on the content of the second in width?

Question

css

Hello, the following problem appeared, to which I could not find an answer, so I want to ask experienced people for advice.
There is a container for two blocks, the first of which is search block #1 and the second block is for icons #2.
it is necessary to make the layout with the expectation that if the number of icons is reduced or added in the second block, the first block would automatically adjust its width.

If anyone knows how this is implemented, please help with advice. If possible, a cross-browser solution is desirable.
Thanks in advance

Answer 1

Here is an example
Try adding icons to see the result

Answer 2

display:table for the parent, and then a fixed-width display:table-cell for one of the columns