[libcxx] Make format specifiers more portable

[bcain]

Summary

These printf()s fail to compile on hexagon.

[• Quuxplusone]

Looks great to me, but this diff affects Microsoft code where @STL_MSFT wrote the upstream version and @Mordante copied/maintains the fork here, so I think they both need to approve this too.

[STL_MSFT]

The microsoft/STL repo follows a convention of always avoiding functional-style C-semantics casts like size_t(value), so these should be static_cast<size_t>(value). (The rationale is that size_t(value) is willing to reinterpret pointer values and is difficult to search for.)

Separately, I am not a huge fan of the size_t type here - it introduces machine-bitness-variation that's unrelated to these values (which are always 32-bit). That said, there's no danger and minimal risk of confusion, and there aren't great alternatives, so I'll live with it.

Thanks for fixing these warnings!

[Mordante]

Please upload the next version with @STL_MSFT's comments addressed with the complete context. Having the complete context makes reviewing easier.

[STL_MSFT]

Looks good to me, thanks.

[• Quuxplusone]

@Mordante LGTY, right?

[Mordante]

In D120532#3350260, @Quuxplusone wrote:

@Mordante LGTY, right?

Yes LGTM!

libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp

if (argc == 1) {
         printf("Loaded seed data from %s.\n", filename);
     } else {
         puts("ERROR: Too many command-line arguments.");
         abort();
     }
 
     puts("SEED DATA:");
     for (const auto& elem : vec) {
-        printf("%u ", elem);
+        printf("%zu ", static_cast<size_t>(elem));
     }
     printf("\n");
 
     seed_seq seq(vec.cbegin(), vec.cend());
 
     mt64.seed(seq);
 
     puts("Successfully seeded mt64. First three values:");
void all_integer_tests() {
     test_from_chars<int>("-2147483647", 10, 11, errc{}, -2147483647); // risky with good digit
     test_from_chars<int>("-2147483648", 10, 11, errc{}, -2147483647 - 1); // risky with max digit
     test_from_chars<int>("-2147483649", 10, 11, out_ran); // risky with bad digit
     test_from_chars<int>("-2147483650", 10, 11, out_ran); // beyond risky
 }
 
 void assert_message_bits(const bool b, const char* const msg, const uint32_t bits) {
     if (!b) {
-        fprintf(stderr, "%s failed for 0x%08X\n", msg, bits);
+        fprintf(stderr, "%s failed for 0x%08zX\n", msg, static_cast<size_t>(bits));
         fprintf(stderr, "This is a randomized test.\n");
         fprintf(stderr, "DO NOT IGNORE/RERUN THIS FAILURE.\n");
         fprintf(stderr, "You must report it to the STL maintainers.\n");
         abort();
     }
 }
 
 void assert_message_bits(const bool b, const char* const msg, const uint64_t bits) {
int main(int argc, char** argv) {
     all_integer_tests();
 
     all_floating_tests(mt64);
 
     const auto finish  = chrono::steady_clock::now();
     const long long ms = chrono::duration_cast<chrono::milliseconds>(finish - start).count();
 
     puts("PASS");
-    printf("Randomized test cases: %u\n", PrefixesToTest * Fractions);
+    printf("Randomized test cases: %zu\n", static_cast<size_t>(PrefixesToTest * Fractions));
     printf("Total time: %lld ms\n", ms);
 
     if (ms < 3'000) {
         puts("That was fast. Consider tuning PrefixesToTest and FractionBits to test more cases.");
     } else if (ms > 30'000) {
         puts("That was slow. Consider tuning PrefixesToTest and FractionBits to test fewer cases.");
     }
 }