Re: [PATCH 2/2] RISC-V: Check for conflicting extensions when the linker merges arch attributes

Oh, okay, I see the case: inputs with 'c' and inputs with 'd' will need zcd
after merging.  Looks reasonable to call riscv_parse_add_implicit_subsets
for merged string, too.

Thanks
Nelson

On Tue, Jul 7, 2026 at 9:19 AM Nelson Chu <[email protected]> wrote:

>
>
> On Mon, Jul 6, 2026 at 7:46 PM Ethan Y. C. Liang <[email protected]>
> wrote:
>
>> The linker validates the arch of each input when parsing it, but never
>> checks the merged arch as a whole, so conflicting extensions could
>> silently slip through.  The merge can even imply extensions that
>> neither input implies alone, e.g. `c' from one input and `d' from
>> another imply `zcd', which conflicts with `zcmp'.
>>
>> After merging the input archs, add the implicit extensions to the
>> merged arch, then run the conflict checks on it and reject the merge
>> if any conflict is found.  Add tests for such merges.
>> ---
>>  bfd/elfxx-riscv.c                                      | 8 ++++++++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d  | 5 +++++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l  | 2 ++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d  | 5 +++++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l  | 2 ++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d  | 5 +++++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l  | 2 ++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d  | 5 +++++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l  | 2 ++
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s | 1 +
>>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s | 1 +
>>  ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp             | 4 ++++
>>  18 files changed, 48 insertions(+)
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
>>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
>>
>> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
>> index fa2f1759f31..128c0eda8c4 100644
>> --- a/bfd/elfxx-riscv.c
>> +++ b/bfd/elfxx-riscv.c
>> @@ -3750,6 +3750,14 @@ riscv_merge_arch_attr_info (bfd *ibfd, char
>> *in_arch, char *out_arch,
>>        goto cleanup;
>>      }
>>
>> +  /* Add the implicit subsets implied by the merged subset list, then
>> +     check if the result is conflicting.  */
>> +  riscv_parse_subset_t riscv_rps_ld_merged =
>> +    {&merged_subsets, _bfd_error_handler, &xlen_in, NULL, false};
>
> +  riscv_parse_add_implicit_subsets (&riscv_rps_ld_merged);
>> +  if (!riscv_parse_check_conflicts (&riscv_rps_ld_merged))
>> +    goto cleanup;
>> +
>>
>
> Looks reasonable to call riscv_parse_check_conflicts for the merged
> architecture string.  But do we need to call
> riscv_parse_add_implicit_subsets?  Since I checked all current
> check_implicit_* functions (always/for_i/for_zcf/for_zcd), I think all
> implicit extensions should be added in the each input object already.
>
> Thanks
> Nelson
>
>
>>    /* Free the previous merged_arch_str which called xmalloc.  */
>>    free (merged_arch_str);
>>
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
>> new file mode 100644
>> index 00000000000..f99677cb767
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
>> @@ -0,0 +1,5 @@
>> +#source: attr-merge-arch-failed-01a.s
>> +#source: attr-merge-arch-failed-01b.s
>> +#as: -mabi=ilp32
>> +#ld: -r -m[riscv_choose_ilp32_emul]
>> +#error_output: attr-merge-arch-failed-01.l
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
>> new file mode 100644
>> index 00000000000..ad6d2630211
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
>> @@ -0,0 +1,2 @@
>> +.*: `zfinx' conflicts with the `f/d/q/zfh/zfhmin' extension
>> +.*: failed to merge target specific data of file .*
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
>> new file mode 100644
>> index 00000000000..8f2a98f95f3
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32i_zfinx"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
>> new file mode 100644
>> index 00000000000..a44b2a0d346
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32if"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
>> new file mode 100644
>> index 00000000000..4fb1980c97d
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
>> @@ -0,0 +1,5 @@
>> +#source: attr-merge-arch-failed-02a.s
>> +#source: attr-merge-arch-failed-02b.s
>> +#as: -mabi=ilp32
>> +#ld: -r -m[riscv_choose_ilp32_emul]
>> +#error_output: attr-merge-arch-failed-02.l
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
>> new file mode 100644
>> index 00000000000..930e03123e1
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
>> @@ -0,0 +1,2 @@
>> +.*: zcmp' is incompatible with `d' and `c', or `zcd' extension
>> +.*: failed to merge target specific data of file .*
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
>> new file mode 100644
>> index 00000000000..3f79059d5d0
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32i_zcmp"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
>> new file mode 100644
>> index 00000000000..95bfe1f6d9f
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32i_zcd"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
>> new file mode 100644
>> index 00000000000..def49c3fb3f
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
>> @@ -0,0 +1,5 @@
>> +#source: attr-merge-arch-failed-03a.s
>> +#source: attr-merge-arch-failed-03b.s
>> +#as: -mabi=ilp32
>> +#ld: -r -m[riscv_choose_ilp32_emul]
>> +#error_output: attr-merge-arch-failed-03.l
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
>> new file mode 100644
>> index 00000000000..d9075d0c30e
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
>> @@ -0,0 +1,2 @@
>> +.*: `zclsd' conflicts with the `c\+f'/`zcf' extension
>> +.*: failed to merge target specific data of file .*
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
>> new file mode 100644
>> index 00000000000..f7f9ceb11f6
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32i_zclsd"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
>> new file mode 100644
>> index 00000000000..f18129dc55d
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32i_zcf"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
>> new file mode 100644
>> index 00000000000..5445936df44
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
>> @@ -0,0 +1,5 @@
>> +#source: attr-merge-arch-failed-04a.s
>> +#source: attr-merge-arch-failed-04b.s
>> +#as: -mabi=ilp32
>> +#ld: -r -m[riscv_choose_ilp32_emul]
>> +#error_output: attr-merge-arch-failed-04.l
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
>> new file mode 100644
>> index 00000000000..930e03123e1
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
>> @@ -0,0 +1,2 @@
>> +.*: zcmp' is incompatible with `d' and `c', or `zcd' extension
>> +.*: failed to merge target specific data of file .*
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
>> new file mode 100644
>> index 00000000000..e79c25b7828
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32ic"
>> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
>> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
>> new file mode 100644
>> index 00000000000..c7468e4e072
>> --- /dev/null
>> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
>> @@ -0,0 +1 @@
>> +       .attribute arch, "rv32id_zcmp"
>> diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
>> b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
>> index 8e26ccff10a..57f3139c9f6 100644
>> --- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
>> +++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
>> @@ -157,6 +157,10 @@ if [istarget "riscv*-*-*"] {
>>      run_dump_test "attr-merge-arch-01"
>>      run_dump_test "attr-merge-arch-02"
>>      run_dump_test "attr-merge-arch-03"
>> +    run_dump_test "attr-merge-arch-failed-01"
>> +    run_dump_test "attr-merge-arch-failed-02"
>> +    run_dump_test "attr-merge-arch-failed-03"
>> +    run_dump_test "attr-merge-arch-failed-04"
>>      run_dump_test "attr-merge-strict-align-01"
>>      run_dump_test "attr-merge-strict-align-02"
>>      run_dump_test "attr-merge-strict-align-03"
>> --
>> 2.54.0
>>
>>