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

[Jason Merrill via Gcc-patches]

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