[libc-commits] [libc] Add bit width length modifier to printf (PR #82461)

[Michael Jones via libc-commits]

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@@ -40,6 +42,18 @@ LIBC_INLINE uintmax_t apply_length_modifier(uintmax_t num, LengthModifier lm) {
     return num & cpp::numeric_limits<uintptr_t>::max();
   case LengthModifier::j:
     return num; // j is intmax, so no mask is necessary.
+  case LengthModifier::w:
+  case LengthModifier::wf: {
+    uintmax_t mask;
+    if (bw == 0) {
+      mask = 0;
+    } else if (bw < sizeof(uintmax_t) * 8) {
+      mask = (static_cast<uintmax_t>(1) << bw) - 1;
+    } else {
+      mask = UINTMAX_MAX;
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michaelrj-google wrote:

you should add a test that checks this behavior

https://github.com/llvm/llvm-project/pull/82461