[PATCH] ipa-devirt: check precision mismatch of enum values [PR101396]

[Richard Sandiford]

Xi Ruoyao via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> We are comparing enum values (in wide_int) to check ODR violation.
> However, if we compare two wide_int values with different precision,
> we'll trigger an assert, leading to ICE.  With enum-base introduced
> in C++11, it's easy to sink into this situation.
>
> To fix the issue, we need to explicitly check this kind of mismatch,
> and emit a proper warning message if there is such one.
>
> Bootstrapped & regtested on x86_64-linux-gnu.  Ok for trunk?
>
> gcc/
>
> 	PR ipa/101396
> 	* ipa-devirt.c (ipa_odr_read_section): Compare the precision of
> 	  enum values, and emit a warning if they mismatch.

OK, thanks.

Richard

> gcc/testsuite/
>
> 	PR ipa/101396
> 	* g++.dg/lto/pr101396_0.C: New test.
> 	* g++.dg/lto/pr101396_1.C: New test.
> ---
>  gcc/ipa-devirt.c                      |  9 +++++++++
>  gcc/testsuite/g++.dg/lto/pr101396_0.C | 12 ++++++++++++
>  gcc/testsuite/g++.dg/lto/pr101396_1.C | 10 ++++++++++
>  3 files changed, 31 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/lto/pr101396_0.C
>  create mode 100644 gcc/testsuite/g++.dg/lto/pr101396_1.C
>
> diff --git a/gcc/ipa-devirt.c b/gcc/ipa-devirt.c
> index 8cd1100aba9..8deec75b2df 100644
> --- a/gcc/ipa-devirt.c
> +++ b/gcc/ipa-devirt.c
> @@ -4193,6 +4193,8 @@ ipa_odr_read_section (struct lto_file_decl_data *file_data, const char *data,
>  	      if (do_warning != -1 || j >= this_enum.vals.length ())
>  		continue;
>  	      if (strcmp (id, this_enum.vals[j].name)
> +		  || (val.get_precision() !=
> +		      this_enum.vals[j].val.get_precision())
>  		  || val != this_enum.vals[j].val)
>  		{
>  		  warn_name = xstrdup (id);
> @@ -4260,6 +4262,13 @@ ipa_odr_read_section (struct lto_file_decl_data *file_data, const char *data,
>  			    "name %qs differs from name %qs defined"
>  			    " in another translation unit",
>  			    this_enum.vals[j].name, warn_name);
> +		  else if (this_enum.vals[j].val.get_precision() !=
> +			   warn_value.get_precision())
> +		    inform (this_enum.vals[j].locus,
> +			    "name %qs is defined as %u-bit while another "
> +			    "translation unit defines it as %u-bit",
> +			    warn_name, this_enum.vals[j].val.get_precision(),
> +			    warn_value.get_precision());
>  		  /* FIXME: In case there is easy way to print wide_ints,
>  		     perhaps we could do it here instead of overflow check.  */
>  		  else if (wi::fits_shwi_p (this_enum.vals[j].val)
> diff --git a/gcc/testsuite/g++.dg/lto/pr101396_0.C b/gcc/testsuite/g++.dg/lto/pr101396_0.C
> new file mode 100644
> index 00000000000..b7a2947a880
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/lto/pr101396_0.C
> @@ -0,0 +1,12 @@
> +/* { dg-lto-do link } */
> +
> +enum A : __UINT32_TYPE__ { // { dg-lto-warning "6: type 'A' violates the C\\+\\+ One Definition Rule" }
> +  a, // { dg-lto-note "3: name 'a' is defined as 32-bit while another translation unit defines it as 64-bit" }
> +  b,
> +  c
> +};
> +
> +int main()
> +{
> +  return (int) A::a;
> +}
> diff --git a/gcc/testsuite/g++.dg/lto/pr101396_1.C b/gcc/testsuite/g++.dg/lto/pr101396_1.C
> new file mode 100644
> index 00000000000..a6d032d694d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/lto/pr101396_1.C
> @@ -0,0 +1,10 @@
> +enum A : __UINT64_TYPE__ { // { dg-lto-note "6: an enum with different value name is defined in another translation unit" }
> +  a, // { dg-lto-note "3: mismatching definition" }
> +  b,
> +  c
> +};
> +
> +int f(enum A x)
> +{
> +  return (int) x;
> +}