[clang] [llvm] [Sema] Implement support for -Wformat-signedness (PR #74440)

[Aaron Ballman via llvm-commits]

================
@@ -0,0 +1,223 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -verify -Wformat -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -std=c11 -fsyntax-only -verify -Wformat -Wformat-signedness %s
+
+// Verify that -Wformat-signedness alone (without -Wformat) trigger the
+// warnings. Note in gcc this will not trigger the signedness warnings as
+// -Wformat is default off in gcc.
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -verify -Wformat-signedness %s
+// RUN: %clang_cc1 -triple=x86_64-pc-win32 -std=c11 -fsyntax-only -verify -Wformat-signedness %s
+
+// Verify that -Wformat-signedness warnings are not reported with only -Wformat
+// (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wformat -Werror %s
+
+// Verify that -Wformat-signedness with -Wno-format are not reported (gcc compat).
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wformat-signedness -Wno-format -Werror %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -std=c11 -fsyntax-only -Wno-format -Wformat-signedness -Werror %s
+
+#include <limits.h>
+
+int printf(const char *restrict format, ...);
+int scanf(const char * restrict, ...);
+
+void test_printf_bool(_Bool x)
+{
+    printf("%d", x); // no-warning
+    printf("%u", x); // no-warning
+    printf("%x", x); // no-warning
+}
+
+void test_printf_char(char x)
+{
+    printf("%c", x); // no-warning
+}
+
+void test_printf_unsigned_char(unsigned char x)
+{
+    printf("%c", x); // no-warning
+}
+
+void test_printf_int(int x)
+{
+    printf("%d", x); // no-warning
+    printf("%u", x); // expected-warning{{format specifies type 'unsigned int' but the argument has type 'int'}}
+    printf("%x", x); // expected-warning{{format specifies type 'unsigned int' but the argument has type 'int'}}
+}
+
+void test_printf_unsigned(unsigned x)
+{
+    printf("%d", x); // expected-warning{{format specifies type 'int' but the argument has type 'unsigned int'}}
+    printf("%u", x); // no-warning
+    printf("%x", x); // no-warning
+}
+
+void test_printf_long(long x)
+{
+    printf("%ld", x); // no-warning
+    printf("%lu", x); // expected-warning{{format specifies type 'unsigned long' but the argument has type 'long'}}
+    printf("%lx", x); // expected-warning{{format specifies type 'unsigned long' but the argument has type 'long'}}
+}
+
+void test_printf_unsigned_long(unsigned long x)
+{
+    printf("%ld", x); // expected-warning{{format specifies type 'long' but the argument has type 'unsigned long'}}
+    printf("%lu", x); // no-warning
+    printf("%lx", x); // no-warning
+}
+
+void test_printf_long_long(long long x)
+{
+    printf("%lld", x); // no-warning
+    printf("%llu", x); // expected-warning{{format specifies type 'unsigned long long' but the argument has type 'long long'}}
+    printf("%llx", x); // expected-warning{{format specifies type 'unsigned long long' but the argument has type 'long long'}}
+}
+
+void test_printf_unsigned_long_long(unsigned long long x)
+{
+    printf("%lld", x); // expected-warning{{format specifies type 'long long' but the argument has type 'unsigned long long'}}
+    printf("%llu", x); // no-warning
+    printf("%llx", x); // no-warning
+}
+
+enum enum_int {
+    minus_1 = -1
+};
+
+void test_printf_enum_int(enum enum_int x)
+{
+    printf("%d", x); // no-warning
+    printf("%u", x); // expected-warning{{format specifies type 'unsigned int' but the argument has underlying type 'int'}}
+    printf("%x", x); // expected-warning{{format specifies type 'unsigned int' but the argument has underlying type 'int'}}
+}
+
+#ifndef _WIN32 // Disabled due to enums have different underlying type on _WIN32
+enum enum_unsigned {
+    zero = 0
+};
+
+void test_printf_enum_unsigned(enum enum_unsigned x)
+{
+    printf("%d", x); // expected-warning{{format specifies type 'int' but the argument has underlying type 'unsigned int'}}
+    printf("%u", x); // no-warning
+    printf("%x", x); // no-warning
+}
+
+enum enum_long {
+    minus_one = -1,
+    int_val = INT_MAX,
+    unsigned_val = (unsigned)INT_MIN
----------------
AaronBallman wrote:

```suggestion
    int_val = __INT_MAX__,
    unsigned_val = (unsigned)(-__INT_MAX__ - 1)
```

https://github.com/llvm/llvm-project/pull/74440