[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, 2 insertions, 2 deletions

diff --git a/llvm/tools/llvm-readobj/ObjDumper.cpp b/llvm/tools/llvm-readobj/ObjDumper.cpp
index 17675fd8f27..a725140c9d3 100644
--- a/llvm/tools/llvm-readobj/ObjDumper.cpp
+++ b/llvm/tools/llvm-readobj/ObjDumper.cpp
@@ -29,7 +29,7 @@ ObjDumper::~ObjDumper() {
 
 static void printAsPrintable(raw_ostream &W, const uint8_t *Start, size_t Len) {
   for (size_t i = 0; i < Len; i++)
-    W << (isprint(Start[i]) ? static_cast<char>(Start[i]) : '.');
+    W << (isPrint(Start[i]) ? static_cast<char>(Start[i]) : '.');
 }
 
 static Expected<object::SectionRef>
@@ -138,7 +138,7 @@ void ObjDumper::printSectionAsHex(const object::ObjectFile *Obj,
 
     TmpSecPtr = SecPtr;
     for (i = 0; TmpSecPtr + i < SecEnd && i < 16; ++i)
-      W.startLine() << (isprint(TmpSecPtr[i]) ? static_cast<char>(TmpSecPtr[i])
+      W.startLine() << (isPrint(TmpSecPtr[i]) ? static_cast<char>(TmpSecPtr[i])
                                               : '.');
 
     W.startLine() << '\n';