Is learning C really a must for a programmer?

Many have this opinion. Somehow, by doing manual memory management allocation and garbage mangement one would become a better programmer.

I have little experience in C mainly because I can write terser and more readable code in Racket or Haskell. However I'm willing to give C a try just to learn these lessons that everybody keeps talking.

But I have a sneaking suspicion that I already know most of what is there to know. Can you list some useful lessons that a typical high level code dweller would be oblivious of?

Cudder thats crazy talk, some optimizations are obviously premature because other optimizations should precede it in priority.

TeX source code ... TDWTF.
(　≖‿≖)

If I remember correctly, there isn't a single instance of dynamic allocation
Well, sorta...

@* \[9] Dynamic memory allocation.
The \TeX\ system does nearly all of its own memory allocation, so that it
can readily be transported into environments that do not have automatic
facilities for strings, garbage collection, etc., and so that it can be in
control of what error messages the user receives. The dynamic storage
requirements of \TeX\ are handled by providing a large array |mem| in
which consecutive blocks of words are used as nodes by the \TeX\ routines.

Pointer variables are indices into this array, or into another array
called |eqtb| that will be explained later. A pointer variable might
also be a special flag that lies outside the bounds of |mem|, so we
allow pointers to assume any |halfword| value. The minimum halfword
value represents a null pointer. \TeX\ does not assume that |mem[null]| exists.
Does Standard Pascal really not have dynamic memory or was Knuth aiming to get TeX working on microcontrollers?