[libc-commits] [libc] [libc] Support %lc in printf (PR #169301)

[via libc-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Shubh Pachchigar (shubhe25p)

<details>
<summary>Changes</summary>

Add %lc support to libc printf by utilizing wctomb internal function, also added relevant unit tests. Resolves #<!-- -->166598 

---
Full diff: https://github.com/llvm/llvm-project/pull/169301.diff


3 Files Affected:

- (modified) libc/src/stdio/printf_core/char_converter.h (+19-3) 
- (modified) libc/test/src/stdio/printf_core/CMakeLists.txt (+2) 
- (modified) libc/test/src/stdio/printf_core/converter_test.cpp (+51) 


``````````diff
diff --git a/libc/src/stdio/printf_core/char_converter.h b/libc/src/stdio/printf_core/char_converter.h
index fd2eb2553887a..58ade4fbf9a53 100644
--- a/libc/src/stdio/printf_core/char_converter.h
+++ b/libc/src/stdio/printf_core/char_converter.h
@@ -13,6 +13,7 @@
 #include "src/stdio/printf_core/converter_utils.h"
 #include "src/stdio/printf_core/core_structs.h"
 #include "src/stdio/printf_core/writer.h"
+#include "src/wchar/wctomb.h"
 
 namespace LIBC_NAMESPACE_DECL {
 namespace printf_core {
@@ -20,8 +21,10 @@ namespace printf_core {
 template <WriteMode write_mode>
 LIBC_INLINE int convert_char(Writer<write_mode> *writer,
                              const FormatSection &to_conv) {
-  char c = static_cast<char>(to_conv.conv_val_raw);
-
+  char c;
+  wchar_t wc;
+  char mb_str[MB_LEN_MAX];
+  int ret = 0;
   constexpr int STRING_LEN = 1;
 
   size_t padding_spaces =
@@ -33,7 +36,20 @@ LIBC_INLINE int convert_char(Writer<write_mode> *writer,
     RET_IF_RESULT_NEGATIVE(writer->write(' ', padding_spaces));
   }
 
-  RET_IF_RESULT_NEGATIVE(writer->write(c));
+  if (to_conv.length_modifier == LengthModifier::l) {
+    wc = static_cast<wchar_t>(to_conv.conv_val_raw);
+    ret = wctomb(mb_str, wc);
+    if (ret <= 0) {
+      return INT_CONVERSION_ERROR;
+    }
+    for (int i = 0; i < ret; ++i) {
+      RET_IF_RESULT_NEGATIVE(writer->write(mb_str[i]));
+    }
+  }
+  else {
+    c = static_cast<char>(to_conv.conv_val_raw);
+    RET_IF_RESULT_NEGATIVE(writer->write(c));
+  }
 
   // If the padding is on the right side, write the spaces last.
   if (padding_spaces > 0 &&
diff --git a/libc/test/src/stdio/printf_core/CMakeLists.txt b/libc/test/src/stdio/printf_core/CMakeLists.txt
index ff7ebbc4f5fd0..f075b8bd5ec52 100644
--- a/libc/test/src/stdio/printf_core/CMakeLists.txt
+++ b/libc/test/src/stdio/printf_core/CMakeLists.txt
@@ -35,4 +35,6 @@ add_libc_unittest(
     libc.src.stdio.printf_core.converter
     libc.src.stdio.printf_core.writer
     libc.src.stdio.printf_core.core_structs
+    libc.src.wchar.wctomb
+    libc.hdr.types.wchar_t
 )
diff --git a/libc/test/src/stdio/printf_core/converter_test.cpp b/libc/test/src/stdio/printf_core/converter_test.cpp
index 2dae2a22c864c..2f7842fa97168 100644
--- a/libc/test/src/stdio/printf_core/converter_test.cpp
+++ b/libc/test/src/stdio/printf_core/converter_test.cpp
@@ -255,3 +255,54 @@ TEST_F(LlvmLibcPrintfConverterTest, OctConversion) {
   ASSERT_STREQ(str, "1234");
   ASSERT_EQ(writer.get_chars_written(), size_t{4});
 }
+
+TEST_F(LlvmLibcPrintfConverterTest, WideCharConversion) {
+
+  LIBC_NAMESPACE::printf_core::FormatSection section;
+  section.has_conv = true;
+  section.raw_string = "%c";
+  section.conv_name = 'c';
+  section.length_modifier = LIBC_NAMESPACE::printf_core::LengthModifier::l;
+  section.conv_val_raw = static_cast<wchar_t>(L'S');
+
+  LIBC_NAMESPACE::printf_core::convert(&writer, section);
+
+  wb.buff[wb.buff_cur] = '\0';
+
+  ASSERT_STREQ(str, "S");
+  ASSERT_EQ(writer.get_chars_written(), size_t{1});
+}
+
+TEST_F(LlvmLibcPrintfConverterTest, WideCharConversionLeftJustified) {
+  LIBC_NAMESPACE::printf_core::FormatSection left_justified_conv;
+  left_justified_conv.has_conv = true;
+  left_justified_conv.raw_string = "%-4c";
+  left_justified_conv.conv_name = 'c';
+  left_justified_conv.length_modifier = LIBC_NAMESPACE::printf_core::LengthModifier::l;
+  left_justified_conv.flags =
+      LIBC_NAMESPACE::printf_core::FormatFlags::LEFT_JUSTIFIED;
+  left_justified_conv.min_width = 4;
+  left_justified_conv.conv_val_raw = static_cast<wchar_t>(L'S');
+
+  LIBC_NAMESPACE::printf_core::convert(&writer, left_justified_conv);
+  wb.buff[wb.buff_cur] = '\0';
+
+  ASSERT_STREQ(str, "S   ");
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
+}
+
+TEST_F(LlvmLibcPrintfConverterTest, WideCharConversionRightJustified) {
+  LIBC_NAMESPACE::printf_core::FormatSection right_justified_conv;
+  right_justified_conv.has_conv = true;
+  right_justified_conv.raw_string = "%4c";
+  right_justified_conv.conv_name = 'c';
+  right_justified_conv.length_modifier = LIBC_NAMESPACE::printf_core::LengthModifier::l;
+  right_justified_conv.min_width = 4;
+  right_justified_conv.conv_val_raw = static_cast<wchar_t>(L'S');
+
+  LIBC_NAMESPACE::printf_core::convert(&writer, right_justified_conv);
+  wb.buff[wb.buff_cur] = '\0';
+
+  ASSERT_STREQ(str, "   S");
+  ASSERT_EQ(writer.get_chars_written(), size_t{4});
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/169301