Sort out locales for OSL (#795)

I got quite the education this week, realizing just how much of C++'s
I/O functionality implicitly takes the system's "locale" into
consideration.  Of particular concern is the conversion of text to
floating point numeric values and vice versa, for which much C++
functionality will happily swap the role of '.' and, say, ',' (comma)
for the decimal mark, depending on the user's country and whether they
are savvy enough to set their locale to the classic "C" (essentially
US-style) version. On the other hand, who can blame somebody for not
blindly accepting US hegemony these days?

But dammit, OSL is a programming language, and so '.' has a specific
role in numeric constants and ',' does something quite different (comma
operator!), and if you start mixing up the two when parsing programs,
it will all end in tears. All other major programming languages just
adopt this convention as well.

Now, if you were writing a full app, you could set the locale to the
classic one globally (to that process) upon startup, and then never
worry about it. Which we can do for oslc itself. But much of OSL is
actually a library that can be embedded into other libraries or apps,
so globally setting the locale can mess up UI internationalization or
the intentional localization of other app I/O. So we have to handle
this deftly throughout.

The fix comes in three parts:

1. I've submitted a separate review to OIIO here:
AcademySoftwareFoundation/OpenImageIO#1785 which tries to straighten
up that library, and in particular the various Strutil and ustring
utilities that we liberally use throughout OSL. And patrol some of the
places where we directly call the locale-sensitive C++ functions like
atof and strtod, and replace them with the now-safe OIIO::Strutil
equivalents. We'll be able to count on all this working for OIIO >= 1.8.6.

2. In a variety of places that don't rely on OIIO (for example, various
outputs via std::ostringstream), we need to take care to explicitly set
the stream's locale to produce the output we expect.

3. For people building OSL against a too-old version of OIIO to contain
the fixes described above, when compiling a buffer of OSL source code,
do the gross but necessary safeguard of saving the prior locale,
globally changing to "C" locale while we compile the OSL, then restoring
the locale.  And *HOPE* that the surrounding application isn't
simultaneously counting on the original locale-based
internationalization still being in effect for something it is doing in
another thread that's unaware that we've temporarily altered a global
setting. That's inherently unsafe, but remember it only affects OSL builds
against pre-1.8 OIIO (once that patch is applied on the OIIO side), and
only will be symptomatic for systems using a non-. locale (which is,
empirically speaking, rare enough that nobody noticed this issue until
this week).

Author: lgritz

src/liboslcomp/oslcomp.cpp

@@ -651,6 +651,7 @@ OSLCompilerImpl::compile_buffer (string_view sourcecode,
             m_output_filename = "<buffer>";
 
             std::ostringstream oso_output;
+            oso_output.imbue (std::locale::classic());  // force C locale
             ASSERT (m_osofile == NULL);
             m_osofile = &oso_output;
 

src/liboslcomp/osllex.l

@@ -98,6 +98,7 @@ CPLUSCOMMENT    \/\/.*\n
 #include <string>
 
 #include <OpenImageIO/thread.h>
+#include <OpenImageIO/strutil.h>
 #include "oslcomp_pvt.h"
 
 using namespace OSL;
@@ -351,13 +352,26 @@ bool
 OSLCompilerImpl::osl_parse_buffer (const std::string &preprocessed_buffer)
 {
     // Thread safety with the lexer/parser
-    static OIIO::mutex oslcompiler_mutex;
-    OIIO::lock_guard lock (oslcompiler_mutex);
+    static std::mutex oslcompiler_mutex;
+    std::lock_guard<std::mutex> lock (oslcompiler_mutex);
+
+#ifndef OIIO_STRUTIL_HAS_STOF
+    // Force classic "C" locale for correct '.' decimal parsing.
+    // N.B. This is not safe in a multi-threaded program where another
+    // application thread is expecting the native locale to work properly.
+    // This is not necessary for versions of OIIO that have Strutil::stof,
+    // and we can remove it entirely when OIIO 1.9 is the minimum.
+    std::locale oldlocale = std::locale::global (std::locale::classic());
+#endif
+
     osl_switch_to_buffer (osl_scan_string (preprocessed_buffer.c_str()));
     oslcompiler = this;
     oslparse ();
     bool parseerr = error_encountered();
     osl_delete_buffer (YY_CURRENT_BUFFER);
+#ifndef OIIO_STRUTIL_HAS_STOF
+    std::locale::global (oldlocale);  // Restore the original locale.
+#endif
     return parseerr;
 }
 

src/liboslexec/instance.cpp

@@ -805,6 +805,7 @@ std::string
 ShaderGroup::serialize () const
 {
     std::ostringstream out;
+    out.imbue (std::locale::classic());  // force C locale
     out.precision (9);
     lock_guard lock (m_mutex);
     for (int i = 0, nl = nlayers(); i < nl; ++i) {

src/liboslexec/osolex.l

@@ -243,7 +243,7 @@ namespace pvt {   // OSL::pvt
 
 
 OSOReader * OSOReader::osoreader = NULL;
-static OIIO::mutex osoread_mutex;
+static std::mutex osoread_mutex;
 
 
 
@@ -252,7 +252,13 @@ OSOReader::parse_file (const std::string &filename)
 {
     // The lexer/parser isn't thread-safe, so make sure Only one thread
     // can actually be reading a .oso file at a time.
-    OIIO::lock_guard guard (osoread_mutex);
+    std::lock_guard<std::mutex> guard (osoread_mutex);
+
+    // Force classic "C" locale for correct '.' decimal parsing.
+    // N.B. This is not safe in a multi-threaded program where another
+    // application thread is expecting the native locale to work properly.
+    std::locale oldlocale;   // save the previous native locale
+    std::locale::global (std::locale::classic());
 
     osoin = OIIO::Filesystem::fopen (filename, "r");
     if (! osoin) {
@@ -271,6 +277,7 @@ OSOReader::parse_file (const std::string &filename)
     }
     oso_delete_buffer (YY_CURRENT_BUFFER);
     fclose (osoin);
+    std::locale::global (oldlocale);  // Restore the original locale.
 
     return ok;
 }
@@ -281,7 +288,16 @@ OSOReader::parse_memory (const std::string &buffer)
 {
     // The lexer/parser isn't thread-safe, so make sure Only one thread
     // can actually be reading a .oso file at a time.
-    OIIO::lock_guard guard (osoread_mutex);
+    std::lock_guard<std::mutex> guard (osoread_mutex);
+
+#ifndef OIIO_STRUTIL_HAS_STOF
+    // Force classic "C" locale for correct '.' decimal parsing.
+    // N.B. This is not safe in a multi-threaded program where another
+    // application thread is expecting the native locale to work properly.
+    // This is not necessary for versions of OIIO that have Strutil::stof,
+    // and we can remove it entirely when OIIO 1.9 is the minimum.
+    std::locale oldlocale = std::locale::global (std::locale::classic());
+#endif
 
     oso_switch_to_buffer (oso_scan_string (buffer.c_str()));
     osoreader = this;
@@ -292,6 +308,9 @@ OSOReader::parse_memory (const std::string &buffer)
         m_err.error ("Failed parse of preloaded OSO code");
     }
     oso_delete_buffer (YY_CURRENT_BUFFER);
+#ifndef OIIO_STRUTIL_HAS_STOF
+    std::locale::global (oldlocale);  // Restore the original locale.
+#endif
 
     return ok;
 }

src/liboslexec/runtimeoptimize.cpp

@@ -807,6 +807,7 @@ OSOProcessorBase::const_value_as_string (const Symbol &A)
     TypeDesc type (A.typespec().simpletype());
     int n = type.numelements() * type.aggregate;
     std::ostringstream s;
+    s.imbue (std::locale::classic());  // force C locale
     if (type.basetype == TypeDesc::FLOAT) {
         for (int i = 0; i < n; ++i)
             s << (i ? "," : "") << ((const float *)A.data())[i];

src/liboslexec/shadingsys.cpp

@@ -1596,6 +1596,7 @@ ShadingSystemImpl::getstats (int level) const
     if (level <= 0)
         return "";
     std::ostringstream out;
+    out.imbue (std::locale::classic());  // force C locale
     out << "OSL ShadingSystem statistics (" << (void*)this;
     out << ") ver " << OSL_LIBRARY_VERSION_STRING
         << ", LLVM " << OSL_LLVM_FULL_VERSION << "\n";

src/oslc/oslcmain.cpp

@@ -112,6 +112,10 @@ static OSLC_ErrorHandler default_oslc_error_handler;
 int
 main (int argc, const char *argv[])
 {
+    // Globally force classic "C" locale, and turn off all formatting
+    // internationalization, for the entire oslc application.
+    std::locale::global (std::locale::classic());
+
     OIIO::Filesystem::convert_native_arguments (argc, (const char **)argv);
 
     std::vector<std::string> args;

src/oslinfo/oslinfo.cpp

@@ -237,6 +237,10 @@ input_file (int argc, const char *argv[])
 int
 main (int argc, char *argv[])
 {
+    // Globally force classic "C" locale, and turn off all formatting
+    // internationalization, for the entire oslinfo application.
+    std::locale::global (std::locale::classic());
+
     OIIO::Filesystem::convert_native_arguments (argc, (const char **)argv);
 
     OIIO::ArgParse ap (argc, (const char **)argv);