[Bug target/94134] New: pdp11-aout puts initial variable into .text section rather than .data

[casner at acm dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94134

            Bug ID: 94134
           Summary: pdp11-aout puts initial variable into .text section
                    rather than .data
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: casner at acm dot org
  Target Milestone: ---

The assembler output for a C program compiled for the pdp11-aout target begins
with a .text directive.  If that program begins with a variable that is not
initialized to a nonzero value, that variable will be left if the .text section
rather than being allocated to the .data section.  If the first variable is
initialized to a nonzero value, then a .data directive is inserted after the
.text directive to switch sections.  This bug matters for formats where the
text section is read-only or with split instruction and data spaces.

I selected component target, but I don't know if this problem is specific to
the pdp11-aout target.

Here is a simple example showing this problem:

Command: pdp11-aout-gcc -ffreestanding -nostdlib -S -o zero.s zero.c

static int zero = 0;
static int one = 1;
int main() {}

        .text
        .even

_zero:  .=.+ 02
        .data
        .even
_one:
        .word   01
        .text
        .even
        .globl  _main
_main:
        setd
        seti
        mov     r5,-(sp)
        mov     sp,r5
        jsr     pc,___main
        nop
        mov     (sp)+,r5
        rts     pc

If the first variable is initialized to a nonzero value, the output is correct:

Command: pdp11-aout-gcc -ffreestanding -nostdlib -S -o one.s one.c

static int one = 1;
static int zero = 0;
int main() {}

        .text
        .data
        .even
_one:
        .word   01
        .even

_zero:  .=.+ 02
        .text
        .even
        .globl  _main
_main:
        setd
        seti
        mov     r5,-(sp)
        mov     sp,r5
        jsr     pc,___main
        nop
        mov     (sp)+,r5
        rts     pc

My environment is a macOS host and pdp11-aout target.

GNU C17 (GCC) version 10.0.1 20200303 (experimental) (pdp11-aout)
        compiled by GNU C version 4.2.1 Compatible Apple LLVM 11.0.0
(clang-1100.0.33.17), GMP version 6.1.2, MPFR version 4.0.1, MPC version 1.1.0,
isl version isl-0.20-GMP

Configured with: ../configure --target=pdp11-aout --prefix=/usr/local
--disable-libstdc++-v3 --disable-libssp --disable-libgfortran --disable-libobjc
--disable-libbacktrace --with-gmp=/opt/local/ --with-mpfr=/opt/local/
--with-mpc=/opt/local/