Using gperf to allow switch-case over strings (in c++17)

[Viktor Engelmann]

Hello everyone,

My name is Viktor Engelmann, this is my first message to this mailinglist.

I'm a C++ developer and tried using gperf for generating code that would 
allow me to write a switch-case over strings.
This didn't work at first, so I dug into the source that gperf had 
generated and added "constexpr" declarations in a few
places. With that, my switch-case over strings worked! (requires c++17)

So then I went to the gperf sources and added an option %constexpr that 
will generate these "constexpr" declarations.
In the attachment, you will find a patch for the latest git revision of 
gperf, which adds this functionality.

The resulting gperf translates the attached test.gperf to a c++17 source 
code that ALMOST compiles: You still get one
compiler-error, because the user-function "foo" calls the private method 
"Perfect_Hash::hash". If you manually make
that method public, the code compiles, including the switch-case over 
strings!

        g++ --std=c++17 -o test test_public.cpp

I want to address this compiler-error in a future patch, where I want to 
add this function "foo" (with a better name) as
a public method to the generated class, so that the accessibility of 
Perfect_Hash::hash isn't a problem anymore - but
I figured that this should be a separate patch.

Kind regards

Viktor

test.gperf
Description: Text document

test_public.cpp
Description: Text Data

test.cpp
Description: Text Data

gperf_constexpr.diff
Description: Text Data