Adds support for "%v" in absl::StrFormat and related functions for numeric types, including integer and floating point values. Users may now specify %v and have the format specifier deduced. Integer values will print according to %d specifications, unsigned values will use %u, and floating point values will use %g. Note that %v does not work for `char` due to ambiguity regarding the intended output. Please continue to use %c for `char`.

PiperOrigin-RevId: 474658166
Change-Id: Iecae39263e368b27232db440535f2bf7da8d863c

1 files changed, 36 insertions, 13 deletions

diff --git a/absl/strings/internal/str_format/arg.cc b/absl/strings/internal/str_format/arg.cc
index 007e8e83..b0e06bfb 100644
--- a/absl/strings/internal/str_format/arg.cc
+++ b/absl/strings/internal/str_format/arg.cc
@@ -278,12 +278,33 @@ bool ConvertIntImplInnerSlow(const IntDigits &as_digits,
   return true;
 }
 
+template <typename T,
+          typename std::enable_if<(std::is_integral<T>::value &&
+                                   std::is_signed<T>::value) ||
+                                      std::is_same<T, int128>::value,
+                                  int>::type = 0>
+constexpr auto ConvertV(T) {
+  return FormatConversionCharInternal::d;
+}
+
+template <typename T,
+          typename std::enable_if<(std::is_integral<T>::value &&
+                                   std::is_unsigned<T>::value) ||
+                                      std::is_same<T, uint128>::value,
+                                  int>::type = 0>
+constexpr auto ConvertV(T) {
+  return FormatConversionCharInternal::u;
+}
+
 template <typename T>
-bool ConvertIntArg(T v, const FormatConversionSpecImpl conv,
-                   FormatSinkImpl *sink) {
+bool ConvertIntArg(T v, FormatConversionSpecImpl conv, FormatSinkImpl *sink) {
   using U = typename MakeUnsigned<T>::type;
   IntDigits as_digits;
 
+  if (conv.conversion_char() == FormatConversionCharInternal::v) {
+    conv.set_conversion_char(ConvertV(T{}));
+  }
+
   // This odd casting is due to a bug in -Wswitch behavior in gcc49 which causes
   // it to complain about a switch/case type mismatch, even though both are
   // FormatConverionChar.  Likely this is because at this point
@@ -334,8 +355,11 @@ bool ConvertIntArg(T v, const FormatConversionSpecImpl conv,
 }
 
 template <typename T>
-bool ConvertFloatArg(T v, const FormatConversionSpecImpl conv,
-                     FormatSinkImpl *sink) {
+bool ConvertFloatArg(T v, FormatConversionSpecImpl conv, FormatSinkImpl *sink) {
+  if (conv.conversion_char() == FormatConversionCharInternal::v) {
+    conv.set_conversion_char(FormatConversionCharInternal::g);
+  }
+
   return FormatConversionCharIsFloat(conv.conversion_char()) &&
          ConvertFloatImpl(v, conv, sink);
 }
@@ -413,19 +437,18 @@ FloatingConvertResult FormatConvertImpl(long double v,
 }
 
 // ==================== Chars ====================
-IntegralConvertResult FormatConvertImpl(char v,
-                                        const FormatConversionSpecImpl conv,
-                                        FormatSinkImpl *sink) {
+CharConvertResult FormatConvertImpl(char v, const FormatConversionSpecImpl conv,
+                                    FormatSinkImpl *sink) {
   return {ConvertIntArg(v, conv, sink)};
 }
-IntegralConvertResult FormatConvertImpl(signed char v,
-                                        const FormatConversionSpecImpl conv,
-                                        FormatSinkImpl *sink) {
+CharConvertResult FormatConvertImpl(signed char v,
+                                    const FormatConversionSpecImpl conv,
+                                    FormatSinkImpl *sink) {
   return {ConvertIntArg(v, conv, sink)};
 }
-IntegralConvertResult FormatConvertImpl(unsigned char v,
-                                        const FormatConversionSpecImpl conv,
-                                        FormatSinkImpl *sink) {
+CharConvertResult FormatConvertImpl(unsigned char v,
+                                    const FormatConversionSpecImpl conv,
+                                    FormatSinkImpl *sink) {
   return {ConvertIntArg(v, conv, sink)};
 }