RFR: 8263028: Windows build fails due to several treat-warning-as-errors

[Ioi Lam]

On Sun, 21 Mar 2021 04:22:42 GMT, Yi Yang <yyang at openjdk.org> wrote:

> cl.exe(19.28.29334) can not build JDK on windows_x64 because it treats many warnings as errors thus prohibiting further compilation. (See detailed failure logs on JBS)
> 
> 1. methodMatcher.cpp
> 
> cl.exe can not handle advanced usage of sscanf(i.e. regex-like sscanf) correctly. This looks like an msvc compiler bug, it has been there for a long while, so I temporarily disable these warnings in a limited region. Outside of this region, the compiler still treats them as errors. This change does not affect the functionality of MethodMatcher::parse_method_pattern, it can parse class name and method name in a desired manner.
> 
> 2. vm_version_x86.cpp
> 
> Some comments contain characters(Register Trademark) that cannot be represented in the current code page (936). Replacing them with ASCII-characters makes the compiler happy.
> 
> Best Regards,
> Yang

The problem in methodMatcher.cpp is caused by this: 

#define RANGEBASE "\x1\x2\x3\x4\x5\x6\x7\x8\xa\xb\xc\xd\xe\xf" \
    "\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" \
    "\x21\x22\x23\x24\x25\x26\x27\x2a\x2b\x2c\x2d"  .....

where the literal `\x25` is the `%` character. It seems like VC++ tries to interpret the `%` character even when it's inside square brackets, like

      if (1 == sscanf(line, "%1022[[);/" RANGEBASE "]%n", sig+1, &bytes_read)) {
-> 
      if (1 == sscanf(line, "%1022[[);.....#$%&.....]%n", sig+1, &bytes_read)) {
                                             ^

The [C++ reference](https://en.cppreference.com/w/c/io/fscanf) is unclear about how characters like `%` can be escaped inside square brackets (or whether they should be escaped at all). 

Trying to use sscanf for this purpose makes the code hard to understand and non portable. It's better to ditch sscanf and read the characters byte-by-byte. That way, you can get rid of the original `PRAGMA_DISABLE_MSVC_WARNING(4819)` as well.

-------------

PR: https://git.openjdk.java.net/jdk/pull/3107