Re: [PATCH] c-family: ICE with -Wconversion and A ?: B [PR101030]

[Jason Merrill <jason@redhat.com>]

On 3/29/22 16:53, Marek Polacek wrote:
> This patch fixes a crash in conversion_warning on a null expression.
> It is null because the testcase uses the GNU A ?: B extension.  We
> could also use op0 instead of op1 in this case, but it doesn't seem
> to be necessary.

I wonder why we don't represent the extension as

SAVE_EXPR(A) ? SAVE_EXPR(A) : B

so we don't hit this sort of problem.  But the patch is OK.

> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> 	PR c++/101030
> 
> gcc/c-family/ChangeLog:
> 
> 	* c-warn.cc (conversion_warning) <case COND_EXPR>: Don't call
> 	conversion_warning when OP1 is null.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/ext/cond5.C: New test.
> ---
>   gcc/c-family/c-warn.cc           |  2 +-
>   gcc/testsuite/g++.dg/ext/cond5.C | 13 +++++++++++++
>   2 files changed, 14 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/ext/cond5.C
> 
> diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
> index 9025fc1c20e..f24ac5d0539 100644
> --- a/gcc/c-family/c-warn.cc
> +++ b/gcc/c-family/c-warn.cc
> @@ -1300,7 +1300,7 @@ conversion_warning (location_t loc, tree type, tree expr, tree result)
>   	tree op1 = TREE_OPERAND (expr, 1);
>   	tree op2 = TREE_OPERAND (expr, 2);
>   
> -	return (conversion_warning (loc, type, op1, result)
> +	return ((op1 && conversion_warning (loc, type, op1, result))
>   		|| conversion_warning (loc, type, op2, result));
>         }
>   
> diff --git a/gcc/testsuite/g++.dg/ext/cond5.C b/gcc/testsuite/g++.dg/ext/cond5.C
> new file mode 100644
> index 00000000000..a92f28998f9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/cond5.C
> @@ -0,0 +1,13 @@
> +// PR c++/101030
> +// { dg-do compile { target { c++11 } } }
> +// { dg-options "-Wconversion" }
> +
> +template <int N>
> +struct jj {
> +    int ii[N ?: 1];
> +    char c = N ?: 1; // { dg-warning "conversion from .int. to .char. changes value from .300. to " }
> +};
> +
> +int main() {
> +    jj<300> kk;
> +}
> 
> base-commit: 69db6e7f4e1d07bf8f33e93a29139cc16c1e0a2f