make: .SECONDARY target breaks buld - makefile

Question

My target is to generate a file (MyOut.elf) and, if this file is generated, generate other two files (MyOut.s19 and size.txt) that are dependent on the that file.
I'm quite a newbie on makefiles, but I wrote the following:
.DEFAULT_GOAL := full
full: MyOut.elf MyOut.s19 size.txt
#echo TARGET
# Tool invocations
MyOut.s19: MyOut.elf
#echo 'Building S19 : $#'
#echo 'MyOut.s19: MyOut.elf' > MyOut.s19
#echo 'Finished building target: $#'
#echo ' '
size.txt: MyOut.elf
#echo 'Building section size summary : $#'
#echo 'size.txt: MyOut.elf' > size.txt
#echo 'Finished building target: $#'
#echo ' '
all: MyOut.elf
MyOut.elf:
#echo 'Building ELF: $#'
#echo 'MyOut.elf' > MyOut.elf
#echo 'Finished building target: $#'
#echo ' '
.PHONY: full
#.SECONDARY:
Now, if I run make, everything works as expected:
> make
Building ELF: MyOut.elf
Finished building target: MyOut.elf
Building S19 : MyOut.s19
Finished building target: MyOut.s19
Building section size summary : size.txt
Finished building target: size.txt
TARGET
Instead, if I uncomment the last line .SECONDARY:, the dependency chain seems "broken", as it stops after the first target (MyOut.elf):
> del *.elf
> make
Building ELF: MyOut.elf
Finished building target: MyOut.elf
TARGET
Then, if I run make again, the dependent files MyOut.s19 and size.txt are built:
> make
Building S19 : MyOut.s19
Finished building target: MyOut.s19
Building section size summary : size.txt
Finished building target: size.txt
TARGET
So, my questions are:
Why is this happening?
How can I overcome this problem? (Note: I can't remove the .SECONDARY directive, since this is part of a makefile automatically generated by Eclipse)

Answer 1

I found a solution to this: I added a new "dummy" target otherTargets to the prerequisites of the target full:
full: MyOut.elf otherTargets
otherTargets: MyOut.s19 size.txt
Now, when I run make, I get
Building ELF: MyOut.elf
Finished building target: MyOut.elf
Building section size summary : size.txt
Finished building target: size.txt
Building S19 : MyOut.s19
Finished building target: MyOut.s19
And if I run it for the second time, I get
make: Nothing to be done for `full'.
Nonetheless, if I erase the .elf file, the "dependant" files are rebuilt correctly.
The explanation to this I found is related to the GNU make documentation:
If an ordinary file b does not exist, and make considers a target that depends on b, it invariably creates b and then updates the target from b. But if b is an intermediate file, then make can leave well enough alone. It won’t bother updating b, or the ultimate target, unless some prerequisite of b is newer than that target or there is some other reason to update that target.
Therefore, my "intermediate files" MyOut.s19 and size.txt are not rebuilt.
My solution is then working since the target otherTargets is never generating an output file, therefore it always needs update.