[Bug target/50807] New: [avr]

[Bug target/50807] New: [avr]

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

             Bug #: 50807
           Summary: [avr]
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gjl@gcc.gnu.org
                CC: eric.weddington@atmel.com
            Target: avr


The following line of code

const char __attribute__((progmem)) var = "Hallo"[0];

compileds with

avr-g++ progmem.c -S -Os

compiles code that tries to initialize var at run time:

    .section    .text.startup,"ax",@progbits
    .type    _GLOBAL__sub_I_progmem.c, @function
_GLOBAL__sub_I_progmem.c:
    ldi r24,lo8(72)
    sts _ZL3var,r24
    ret
    .size    _GLOBAL__sub_I_progmem.c, .-_GLOBAL__sub_I_progmem.c

    .global __do_global_ctors
    .section .ctors,"a",@progbits
    .word    gs(_GLOBAL__sub_I_progmem.c)
    .local    _ZL3var
    .comm    _ZL3var,1,1

As var is located in flash and thus cannot be initialized at runtime, there
should be an error message like
"progmem variable var cannot be initialized at load time".

[Bug target/50807] [avr]

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P5
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-10-20
   Target Milestone|---                         |4.6.2
     Ever Confirmed|0                           |1
      Known to fail|                            |4.6.2, 4.7.0
           Severity|normal                      |minor

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-10-20 10:16:37 UTC ---
Confirmed with 4.6.2

The generated code is a bit different.
var is put into the correct section .progmem but there is no error and the
constructor will write to RAM:

    .section    .text.startup,"ax",@progbits
    .type    _GLOBAL__sub_I_progmem.c, @function
_GLOBAL__sub_I_progmem.c:
    ldi r24,lo8(72)
    sts _ZL3var,r24
    ret
    .size    _GLOBAL__sub_I_progmem.c, .-_GLOBAL__sub_I_progmem.c

    .global __do_global_ctors
    .section .ctors,"a",@progbits
    .word    gs(_GLOBAL__sub_I_progmem.c)
    .section    .progmem.data,"a",@progbits
    .type    _ZL3var, @object
    .size    _ZL3var, 1
_ZL3var:
    .skip 1,0

[Bug target/50807] [avr] Constructor writing to RAM for variable in Flash

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.2                       |4.6.3

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-10-26 17:13:59 UTC ---
GCC 4.6.2 is being released.

[Bug target/50807] [avr] Constructor writing to RAM for variable in Flash

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.3                       |4.6.4

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-01 14:39:18 UTC ---
GCC 4.6.3 is being released.

[Bug target/50807] [avr] Constructor writing to RAM for variable in Flash

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-12 16:16:16 UTC ---
Is this reproduceable with 4.7.3, 4.8.0 or the trunk?

[Bug target/50807] [avr] Constructor writing to RAM for variable in Flash

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW

--- Comment #5 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #4)
> Is this reproduceable with 4.7.3, 4.8.0 or the trunk?

With the test case from above and 4.8.0, no code is generated at all.

With an extended test case as follows, the constructor still writes to RAM in
insn 6:

const char __attribute__((progmem)) var = "Hallo"[0];

const char *foo (void)
{
    return &var;
}

_GLOBAL__sub_I__Z3foov:
    ldi r24,lo8(72)     ;  5    movqi_insn/2    [length = 1]
    sts _ZL3var,r24     ;  6    movqi_insn/3    [length = 2]
    ret     ;  13    return    [length = 1]

And there is a warning from the back end:

foo.c: In function 'const char* foo()':
foo.c:1:37: warning: uninitialized variable 'var' put into program memory area
[-Wuninitialized]
 const char __attribute__((progmem)) var = "Hallo"[0];

[Bug target/50807] [avr] Constructor writing to RAM for variable in Flash

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |target
   Target Milestone|4.6.4                       |---

[Bug target/50807] [avr] Constructor writing to RAM for variable in Flash

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50807

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
      Known to work|                            |4.9.2
         Resolution|---                         |WORKSFORME
   Target Milestone|---                         |4.9.0

--- Comment #6 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Works in 4.9.