[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, 5 insertions, 4 deletions

diff --git a/libc/src/stdio/printf_core/printf_main.h b/libc/src/stdio/printf_core/printf_main.h
index 57f29858d529..1c7a7237c097 100644
--- a/libc/src/stdio/printf_core/printf_main.h
+++ b/libc/src/stdio/printf_core/printf_main.h
@@ -10,6 +10,7 @@
 #define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_PRINTF_MAIN_H
 
 #include "src/__support/arg_list.h"
+#include "src/__support/error_or.h"
 #include "src/__support/macros/config.h"
 #include "src/stdio/printf_core/converter.h"
 #include "src/stdio/printf_core/core_structs.h"
@@ -22,8 +23,9 @@ namespace LIBC_NAMESPACE_DECL {
 namespace printf_core {
 
 template <WriteMode write_mode>
-int printf_main(Writer<write_mode> *writer, const char *__restrict str,
-                internal::ArgList &args) {
+ErrorOr<size_t> printf_main(Writer<write_mode> *writer,
+                            const char *__restrict str,
+                            internal::ArgList &args) {
   Parser<internal::ArgList> parser(str, args);
   int result = 0;
   for (FormatSection cur_section = parser.get_next_section();
@@ -33,9 +35,8 @@ int printf_main(Writer<write_mode> *writer, const char *__restrict str,
       result = convert(writer, cur_section);
     else
       result = writer->write(cur_section.raw_string);
-
     if (result < 0)
-      return result;
+      return Error(-result);
   }
 
   return writer->get_chars_written();