[Bug c++/99001] New: indirect modification of function parameters

[wolfgang.roehrl@gi-de.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99001

            Bug ID: 99001
           Summary: indirect modification of function parameters
           Product: gcc
           Version: 7.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wolfgang.roehrl@gi-de.com
  Target Milestone: ---

Hi,
I would like to post a bug report for the GNU C/C++ compiler 7.5.0.
We use the compiler to generate code for a PowerPC processor.

Invokation line for the GNU C++ compiler:
ccppc -c -x c++ --std=gnu++17 -Wall -Werror -g -mcpu=e6500 -m32
      -maltivec -mvrsave -ftls-model=local-exec -msdata=sysv
      -fno-common -fno-openmp -mbig -mmultiple -mno-string -misel
      -mstrict-align -fverbose-asm -G 8 -O3
      -I<some include paths>
      -D<some #define's>
      X.CPP -oX.O

// file X.CPP

struct X
{
    X (int& r) : rr(r) {}
    ~X () { rr = 0; }

    int& rr;
};

int f1 (int i)
{
    { X x(i); }
    return i;
}

int f2 (int i)
{
    X x(i);
    return i;
}

Wenn we compile this program the functions do the following:
- function f1() returns 0 - independently of the value of parameter i;
- function f2() returns the unmodified value of parameter i.

I think that the behaviour of f2() is wrong and f2() should behave as
function f1() does.

With kind regards
W. Roehrl