[Bug c/84163] New: [avr] Allow address space qualifier for compound literals

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84163

            Bug ID: 84163
           Summary: [avr] Allow address space qualifier for compound
                    literals
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gjl at gcc dot gnu.org
  Target Milestone: ---

avr-gcc currently accepts address-space qualifiers in compound literals
provided this is outside of a function:

#define FSTR(X) ((const __flash char[]) { X } )

const __flash char *pet = FSTR ("pet");

$ avr-gcc literal.c -S -mmcu=atmega8

        .section        .progmem.data,"a",@progbits
        .type   __compound_literal.0, @object
        .size   __compound_literal.0, 4
__compound_literal.0:
        .string "pet"
.global pet
        .data
        .type   pet, @object
        .size   pet, 2
pet:
        .word   __compound_literal.0


Hence this works great and perfectly as expected.  Unfortunately, this does not
work locally in a function:

const __flash char* get_pet (void)
{
  static const __flash char *pet = FSTR ("pet");
  return pet;
}

literal.c: In function 'get_pet':
literal.c:7:3: error: compound literal qualified by address-space qualifier
   static const __flash char *pet = FSTR ("pet");
   ^~~~~~


Would be great if the C front end also supported such compound literals with
the obvious semantics as a GNU-C extension (which __flash and other
address-spaces already are).