inconsistent results from isprint('\t') #7416
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One potential fix might be to use Unicode character categories, as suggested in #5939. |
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Note that our current |
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See also this discussion, in which the MinGW developers comment that contrery [sic] to other systems,msvcrt DLL version of iswprint function returns 1 for tab character and hence specifically check for tabs in GDB's |
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I don't think there is a Unicode "printable" property looking at http://www.unicode.org/reports/tr44/#Character_Properties The traditional ASCII printable has meant "not a control or delete", so space was "printable" but tab was not. |
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The tab character in Unicode is in category |
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fixed by #8233 |
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:
JuliaLang/julia#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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@338034 91177308-0d34-0410-b5e6-96231b3b80d8
As mentioned in #7402 and JuliaLang/IJulia.jl#200,
isprint('\t')returnstrueon Windows andfalseon MacOS. This inconsistency seems undesirable.According to http://en.cppreference.com/w/cpp/string/byte/isprint, the correct result is
false. However, other documentation forisprintis vague on the topic. Sinceisprint(' ')returnstrue, it seems odd to me that it would return false for a tab.I'm not sure what the right answer is here, but I'm leaning towards
falsebased on what non-Windows systems do.The text was updated successfully, but these errors were encountered: