[clang] [clang][Sema] Stop format size estimator upon %p to adapt to linux kernel's extension (PR #65969)

[Takuya Shimizu via cfe-commits]

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@@ -96,6 +96,11 @@ void call_snprintf(double d) {
   __builtin_snprintf(buf, 1, "%.1000g", d); // expected-warning {{'snprintf' will always be truncated; specified size is 1, but format string expands to at least 2}}
   __builtin_snprintf(buf, 5, "%.1000g", d);
   __builtin_snprintf(buf, 5, "%.1000G", d);
+  char node_name[6];
+  __builtin_snprintf(node_name, sizeof(node_name), "%pOFn", ptr);
+  __builtin_snprintf(node_name, sizeof(node_name), "12345%pOFn", ptr);
+  __builtin_snprintf(node_name, sizeof(node_name), "123456%pOFn", ptr); // expected-warning {{'snprintf' will always be truncated; specified size is 6, but format string expands to at least 7}}
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hazohelet wrote:

GCC doesn't warn on this ([live demo](https://godbolt.org/z/bEbYx5Gar)). It's probably because GCC even ignores the terminating null char, but I think it makes sense to consider the null char and add 1 (Probably it doesn't matter much, though).

https://github.com/llvm/llvm-project/pull/65969