[Bug bootstrap/101574] gcc/sparseset.h:215:20: error: suggest parentheses around assignment used as truth value [-Werror=parentheses]

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101574

Thomas Schwinge <tschwinge at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marxin at gcc dot gnu.org,
                   |                            |msebor at gcc dot gnu.org
           Keywords|                            |GC

--- Comment #6 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
Short summary: I ran into an unexpected '0xa5a5a5a5' in
'gcc/warning-control.cc', and a search through email archives pointed me to
PR101292, PR101204, which superficially indeed do look similar.

Anybody got a good suggestion about how to proceed here?

---

    (gdb) break c-common.c:3633
    Breakpoint 3 at 0xea31b5: file [...]/source-gcc/gcc/c-family/c-common.c,
line 3633.
    (gdb) r
    [...]
    Breakpoint 3, c_common_truthvalue_conversion (location=2147537812,
expr=0x7ffff3f10550) at [...]/source-gcc/gcc/c-family/c-common.c:3635
    3635          if (!warning_suppressed_p (expr, OPT_Wparentheses)
    (gdb) c
    Continuing.

    Breakpoint 3, c_common_truthvalue_conversion (location=2147537812,
expr=0x7ffff3f105f0) at [...]/source-gcc/gcc/c-family/c-common.c:3635
    3635          if (!warning_suppressed_p (expr, OPT_Wparentheses)
    (gdb) c
    Continuing.

    Breakpoint 3, c_common_truthvalue_conversion (location=2147537909,
expr=0x7ffff3f14be0) at [...]/source-gcc/gcc/c-family/c-common.c:3635
    3635          if (!warning_suppressed_p (expr, OPT_Wparentheses)
    (gdb) s
    warning_suppressed_p (expr=0x7ffff3f14be0, opt=OPT_Wparentheses) at
[...]/source-gcc/gcc/warning-control.cc:119
    119       const nowarn_spec_t *spec = get_nowarn_spec (expr);
    (gdb) s
    get_nowarn_spec (expr=0x7ffff3f14be0) at
[...]/source-gcc/gcc/warning-control.cc:92
    92        const key_type_t key = convert_to_key (expr);
    (gdb) call debug_tree(expr)
     <modify_expr 0x7ffff3f14be0
        type <integer_type 0x7ffff65fc690 unsigned int public unsigned type_6
SI
            size <integer_cst 0x7ffff65ff120 constant 32>
            unit-size <integer_cst 0x7ffff65ff138 constant 4>
            align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff65fc690 precision:32 min <integer_cst 0x7ffff65ff150 0> max <integer_cst
0x7ffff65ff108 4294967295>
            pointer_to_this <pointer_type 0x7ffff660c348> reference_to_this
<reference_type 0x7ffff3ce9d20>>
        side-effects
        arg:0 <view_convert_expr 0x7ffff2f46780 type <integer_type
0x7ffff65fc690 unsigned int>
            tree_2
            arg:0 <view_convert_expr 0x7ffff2f467a0 type <integer_type
0x7ffff65fc690 unsigned int>
                public arg:0 <var_decl 0x7ffff608e6c0 i>
                [...]/source-gcc/gcc/lra-lives.c:304:3 start:
[...]/source-gcc/gcc/lra-lives.c:304:3 finish:
[...]/source-gcc/gcc/lra-lives.c:304:3>
            [...]/source-gcc/gcc/lra-lives.c:304:3 start:
[...]/source-gcc/gcc/lra-lives.c:304:3 finish:
[...]/source-gcc/gcc/lra-lives.c:304:3>
        arg:1 <call_expr 0x7ffff30edd58 type <integer_type 0x7ffff65fc690
unsigned int>
            side-effects nothrow
            fn <addr_expr 0x7ffff2f467c0 type <pointer_type 0x7ffff246bc78>
                constant arg:0 <function_decl 0x7ffff2794c00
sparseset_iter_elm>>
            arg:0 <view_convert_expr 0x7ffff2f467e0 type <pointer_type
0x7ffff278eb28 sparseset>
                public arg:0 <var_decl 0x7ffff60426c0 pseudos_live>
                [...]/source-gcc/gcc/lra-lives.c:304:3 start:
[...]/source-gcc/gcc/lra-lives.c:304:3 finish:
[...]/source-gcc/gcc/lra-lives.c:304:3>
            [...]/source-gcc/gcc/lra-lives.c:304:3 start:
[...]/source-gcc/gcc/lra-lives.c:304:3 finish:
[...]/source-gcc/gcc/lra-lives.c:304:3>
        [...]/source-gcc/gcc/lra-lives.c:304:3 start:
[...]/source-gcc/gcc/lra-lives.c:304:3 finish:
[...]/source-gcc/gcc/lra-lives.c:304:3>
    (gdb) n
    94        if (!get_no_warning_bit (expr) || !key)
    (gdb) print key
    $4 = 2147537909
    (gdb) print/x key
    $5 = 0x8000d3f5
    (gdb) s
    get_no_warning_bit (expr=0x7ffff3f14be0) at
[...]/source-gcc/gcc/warning-control.cc:40
    40        return expr->base.nowarning_flag;
    (gdb) finish
    Run till exit from #0  get_no_warning_bit (expr=0x7ffff3f14be0) at
[...]/source-gcc/gcc/warning-control.cc:40
    0x0000000001d18699 in get_nowarn_spec (expr=0x7ffff3f14be0) at
[...]/source-gcc/gcc/warning-control.cc:94
    94        if (!get_no_warning_bit (expr) || !key)
    Value returned is $6 = true
    (gdb) n
    97        return nowarn_map ? nowarn_map->get (key) : NULL;
    (gdb) print nowarn_map
    $7 = (xint_hash_map_t *) 0x7ffff675ae10
    (gdb) finish
    Run till exit from #0  get_nowarn_spec (expr=0x7ffff3f14be0) at
[...]/source-gcc/gcc/warning-control.cc:97
    0x0000000001d18764 in warning_suppressed_p (expr=0x7ffff3f14be0,
opt=OPT_Wparentheses) at [...]/source-gcc/gcc/warning-control.cc:119
    119       const nowarn_spec_t *spec = get_nowarn_spec (expr);
    Value returned is $8 = (nowarn_spec_t *) 0x7ffff65c66d4
    (gdb) print/x *$8
    $9 = {m_bits = 0xa5a5a5a5}

(This is what then causes the spurious diagnostic; in a "non-faulting" build,
this is 'm_bits = 2'.)