[clang] [Clang] Fix '-Wformat-overflow' FP when floats had field-width and plus prefix (PR #144274)

[Baranov Victor via cfe-commits]

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@@ -43,6 +43,11 @@ void call_snprintf(double d, int n, int *ptr) {
   __builtin_snprintf(node_name, sizeof(node_name), "%pOFn", ptr); // nonkprintf-warning {{'snprintf' will always be truncated; specified size is 6, but format string expands to at least 7}}
   __builtin_snprintf(node_name, sizeof(node_name), "12345%pOFn", ptr); // nonkprintf-warning {{'snprintf' will always be truncated; specified size is 6, but format string expands to at least 12}}
   __builtin_snprintf(node_name, sizeof(node_name), "123456%pOFn", ptr); // nonkprintf-warning {{'snprintf' will always be truncated; specified size is 6, but format string expands to at least 13}}
+  __builtin_snprintf(buf, 6, "%5.1f", 9.f);
+  __builtin_snprintf(buf, 6, "%+5.1f", 9.f);
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vbvictor wrote:

`+` and ` ` are covered here:
https://github.com/llvm/llvm-project/blob/f64d5df3c2524d92b3257ac50cfd941393159f98/clang/test/Sema/format-strings.c#L456-L461
so I suppose we don't need to add more cases

https://github.com/llvm/llvm-project/pull/144274