[libc] Add printf error handling (with fixes #2) (#166517)

https://github.com/llvm/llvm-project/issues/159474

Another try of trying to land
https://github.com/llvm/llvm-project/pull/166382
- Fix some leftover tests checking for specific  errnos
- Guard errno checking tests to not run on the GPU

@michaelrj-google

1 files changed, 10 insertions, 1 deletions

diff --git a/libc/src/stdlib/strfroml.cpp b/libc/src/stdlib/strfroml.cpp
index 12f22a8a2fb6..31668a0323c9 100644
--- a/libc/src/stdlib/strfroml.cpp
+++ b/libc/src/stdlib/strfroml.cpp
@@ -7,7 +7,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/stdlib/strfroml.h"
+#include "src/__support/CPP/limits.h"
 #include "src/__support/macros/config.h"
+#include "src/stdio/printf_core/core_structs.h"
+#include "src/stdio/printf_core/error_mapper.h"
 #include "src/stdlib/str_from_util.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -41,7 +44,13 @@ LLVM_LIBC_FUNCTION(int, strfroml,
   if (n > 0)
     wb.buff[wb.buff_cur] = '\0';
 
-  return writer.get_chars_written();
+  if (writer.get_chars_written() >
+      static_cast<size_t>(cpp::numeric_limits<int>::max())) {
+    libc_errno =
+        printf_core::internal_error_to_errno(-printf_core::OVERFLOW_ERROR);
+    return -1;
+  }
+  return static_cast<int>(writer.get_chars_written());
 }
 
 } // namespace LIBC_NAMESPACE_DECL