[ADT] Replace std::isprint by llvm::isPrint.

The standard library functions ::isprint/std::isprint have platform-
and locale-dependent behavior which makes LLVM's output less
predictable. In particular, regression tests my fail depending on the
implementation of these functions.

Implement llvm::isPrint in StringExtras.h with a standard behavior and
replace all uses of ::isprint/std::isprint by a call it llvm::isPrint.
The function is inlined and does not look up language settings so it
should perform better than the standard library's version.

Such a replacement has already been done for isdigit, isalpha, isxdigit
in r314883. gtest does the same in gtest-printers.cc using the following
justification:

    // Returns true if c is a printable ASCII character.  We test the
    // value of c directly instead of calling isprint(), which is buggy on
    // Windows Mobile.
    inline bool IsPrintableAscii(wchar_t c) {
      return 0x20 <= c && c <= 0x7E;
    }

Similar issues have also been encountered by Julia:
https://github.com/JuliaLang/julia/issues/7416

I noticed the problem myself when on Windows isprint('\t') started to
evaluate to true (see https://stackoverflow.com/questions/51435249) and
thus caused several unit tests to fail. The result of isprint doesn't
seem to be well-defined even for ASCII characters. Therefore I suggest
to replace isprint by a platform-independent version.

Differential Revision: https://reviews.llvm.org/D49680

llvm-svn: 338034

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/unittests/ADT/StringExtrasTest.cpp b/llvm/unittests/ADT/StringExtrasTest.cpp
index f98f388f64f..1df200553a6 100644
--- a/llvm/unittests/ADT/StringExtrasTest.cpp
+++ b/llvm/unittests/ADT/StringExtrasTest.cpp
@@ -13,6 +13,17 @@
 
 using namespace llvm;
 
+TEST(StringExtrasTest, isPrint) {
+  EXPECT_FALSE(isPrint('\0'));
+  EXPECT_FALSE(isPrint('\t'));
+  EXPECT_TRUE(isPrint('0'));
+  EXPECT_TRUE(isPrint('a'));
+  EXPECT_TRUE(isPrint('A'));
+  EXPECT_TRUE(isPrint(' '));
+  EXPECT_TRUE(isPrint('~'));
+  EXPECT_TRUE(isPrint('?'));
+}
+
 TEST(StringExtrasTest, Join) {
   std::vector<std::string> Items;
   EXPECT_EQ("", join(Items.begin(), Items.end(), " <sep> "));
@@ -93,6 +104,13 @@ TEST(StringExtrasTest, printLowerCase) {
   EXPECT_EQ("abcdefg01234.,&!~`'}\"", OS.str());
 }
 
+TEST(StringExtrasTest, printEscapedString) {
+  std::string str;
+  raw_string_ostream OS(str);
+  printEscapedString("ABCdef123&<>\\\"'\t", OS);
+  EXPECT_EQ("ABCdef123&<>\\5C\\22'\\09", OS.str());
+}
+
 TEST(StringExtrasTest, printHTMLEscaped) {
   std::string str;
   raw_string_ostream OS(str);