[libc-commits] [libc] [libc][stdio] Add support for the %m modifier (PR #218312)

[Michael Jones via libc-commits]

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@@ -40,8 +47,27 @@ int convert_string(Reader<T> *reader, const FormatSection &to_conv) {
     }
   }
 
-  char *output = reinterpret_cast<char *>(to_conv.output_ptr);
-
+  char *output;
+#ifndef LIBC_COPT_SCANF_DISABLE_ALLOCATION
+  size_t alloc_size;
+  AllocChecker ac;
+  if ((to_conv.flags & NO_WRITE) == 0 && (to_conv.flags & ALLOCATE) != 0) {
+    if (to_conv.conv_name == 'c')
+      alloc_size = max_width + 1;
+    else
+      alloc_size =
+          (max_width < ALLOCATION_BASE) ? max_width + 1 : ALLOCATION_BASE;
+    output = new (ac) char[alloc_size];
+    if (!ac) {
+      libc_errno = ENOMEM;
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michaelrj-google wrote:

setting errno in an internal function like this isn't allowed in LLVM-libc. Returning the allocation failure error code is enough. Here and below.

https://github.com/llvm/llvm-project/pull/218312