MAINT-4744: Eliminate viewer dependency on (old) GNU libstdc++.

To be more accurate, this changeset doesn't actually eliminate the dependency:
it eliminates the use cases for the llifstream / llofstream feature that
requires it.
Currently you can construct an llifstream or llofstream from an open LLFILE*
file handle (or, except on Windows, an int file descriptor). But rather than
containing a streambuf implementation based on FILE*, llfile.h relies on the
fact that the Windows std::filebuf happens to support that as a nonstandard
extension; also on a nonstandard GNU extension __gnu_cxx::stdio_filebuf<char>.
To move from GNU libstdc++ to clang's libc++ (the direction on Mac), we could
code a streambuf that supports FILE*. But before doing that, it's worth asking
whether anyone actually uses this questionable feature.
In fact there were only two methods: LLWearable::exportFile() and importFile()
-- and only one call to either, in LLViewerWearable::saveNewAsset(). The code
in saveNewAsset() opened the LLFILE* immediately before calling exportFile(),
meaning we could reasonably push the open operation down into exportFile().
That logic was complex anyway due to the need for the caller to close the
LLFILE* regardless of the success of the exportFile().
Change LLWearable::exportFile() and importFile() to accept a std::string
filename rather than an open LLFILE*. Change LLViewerWearable::saveNewAsset()
to simply call exportFile(filename) rather than horsing around with an LLFILE*
handle. (This improves the code in another way too: it encapsulates the need
to open the relevant file in binary mode. Previously, each caller had to
remember to do that.)
To prevent inadvertent reintroduction of ll[io]fstream(LLFILE*) code, add
llstream_LLFILE preprocessor macro (default 0) to control access to the
relevant constructors. Also suppress rdbuf() override, the only method whose
signature references llstdio_filebuf.

indra/llappearance/llwearable.cpp

@@ -86,10 +86,10 @@ LLAssetType::EType LLWearable::getAssetType() const
 	return LLWearableType::getAssetType(mType);
 }
 
-BOOL LLWearable::exportFile(LLFILE* fp) const
+BOOL LLWearable::exportFile(const std::string& filename) const
 {
-	llofstream ofs(fp);
-	return exportStream(ofs);
+	llofstream ofs(filename, std::ios_base::out | std::ios_base::trunc | std::ios_base::binary);
+	return ofs.is_open() && exportStream(ofs);
 }
 
 // virtual
@@ -201,10 +201,11 @@ void LLWearable::createLayers(S32 te, LLAvatarAppearance *avatarp)
 	}
 }
 
-LLWearable::EImportResult LLWearable::importFile(LLFILE* fp, LLAvatarAppearance* avatarp )
+LLWearable::EImportResult LLWearable::importFile(const std::string& filename,
+												 LLAvatarAppearance* avatarp )
 {
-	llifstream ifs(fp);
-	return importStream(ifs, avatarp);
+	llifstream ifs(filename, std::ios_base::in | std::ios_base::binary);
+	return (! ifs.is_open())? FAILURE : importStream(ifs, avatarp);
 }
 
 // virtual

indra/llappearance/llwearable.h

@@ -81,8 +81,8 @@ class LLWearable
 		SUCCESS,
 		BAD_HEADER
 	};
-	BOOL				exportFile(LLFILE* file) const;
-	EImportResult		importFile(LLFILE* file, LLAvatarAppearance* avatarp );
+	BOOL				exportFile(const std::string& filename) const;
+	EImportResult		importFile(const std::string& filename, LLAvatarAppearance* avatarp );
 	virtual BOOL				exportStream( std::ostream& output_stream ) const;
 	virtual EImportResult		importStream( std::istream& input_stream, LLAvatarAppearance* avatarp );
 

indra/llcommon/llfile.cpp

@@ -919,6 +919,7 @@ llifstream::llifstream(const char* _Filename,
 #endif
 
 
+#if llstream_LLFILE
 // explicit
 llifstream::llifstream(_Filet *_File,
 		ios_base::openmode _Mode, size_t _Size) :
@@ -942,6 +943,7 @@ llifstream::llifstream(int __fd,
 	this->init(&_M_filebuf);
 }
 #endif
+#endif // llstream_LLFILE
 
 bool llifstream::is_open() const
 {	// test if C stream has been opened
@@ -1039,6 +1041,7 @@ llofstream::llofstream(const char* _Filename,
 }
 #endif
 
+#if llstream_LLFILE
 // explicit
 llofstream::llofstream(_Filet *_File,
 			ios_base::openmode _Mode, size_t _Size) :
@@ -1062,6 +1065,7 @@ llofstream::llofstream(int __fd,
 	this->init(&_M_filebuf);
 }
 #endif
+#endif // llstream_LLFILE
 
 bool llofstream::is_open() const
 {	// test if C stream has been opened

indra/llcommon/llfile.h

@@ -86,6 +86,12 @@ class LL_COMMON_API LLFile
 	static  const char * tmpdir();
 };
 
+// Remove ll[io]fstream support for [LL]FILE*, preparing to remove dependency
+// on GNU's standard library.
+#if ! defined(llstream_LLFILE)
+#define llstream_LLFILE 0
+#endif
+
 /**
  *  @brief Provides a layer of compatibility for C/POSIX.
  *
@@ -228,6 +234,7 @@ class LL_COMMON_API llifstream	:	public	std::istream
 	explicit llifstream(const char* _Filename,
 			ios_base::openmode _Mode = ios_base::in);
 
+#if llstream_LLFILE
 	/**
 	 *  @brief  Create a stream using an open c file stream.
 	 *  @param  File  An open @c FILE*.
@@ -253,6 +260,7 @@ class LL_COMMON_API llifstream	:	public	std::istream
 			//size_t _Size = static_cast<size_t>(BUFSIZ));
 			size_t _Size = static_cast<size_t>(1));
 #endif
+#endif // llstream_LLFILE
 
 	/**
 	 *  @brief  The destructor does nothing.
@@ -263,6 +271,7 @@ class LL_COMMON_API llifstream	:	public	std::istream
 	virtual ~llifstream() {}
 
 	// Members:
+#if llstream_LLFILE
 	/**
 	 *  @brief  Accessing the underlying buffer.
 	 *  @return  The current basic_filebuf buffer.
@@ -271,6 +280,7 @@ class LL_COMMON_API llifstream	:	public	std::istream
 	*/
 	llstdio_filebuf* rdbuf() const
 	{ return const_cast<llstdio_filebuf*>(&_M_filebuf); }
+#endif // llstream_LLFILE
 
 	/**
 	 *  @brief  Wrapper to test for an open file.
@@ -340,6 +350,7 @@ class LL_COMMON_API llofstream	:	public	std::ostream
 	explicit llofstream(const char* _Filename,
 			ios_base::openmode _Mode = ios_base::out|ios_base::trunc);
 
+#if llstream_LLFILE
 	/**
 	 *  @brief  Create a stream using an open c file stream.
 	 *  @param  File  An open @c FILE*.
@@ -365,6 +376,7 @@ class LL_COMMON_API llofstream	:	public	std::ostream
 			//size_t _Size = static_cast<size_t>(BUFSIZ));
 			size_t _Size = static_cast<size_t>(1));
 #endif
+#endif // llstream_LLFILE
 
 	/**
 	 *  @brief  The destructor does nothing.
@@ -375,6 +387,7 @@ class LL_COMMON_API llofstream	:	public	std::ostream
 	virtual ~llofstream() {}
 
 	// Members:
+#if llstream_LLFILE
 	/**
 	 *  @brief  Accessing the underlying buffer.
 	 *  @return  The current basic_filebuf buffer.
@@ -383,6 +396,7 @@ class LL_COMMON_API llofstream	:	public	std::ostream
 	*/
 	llstdio_filebuf* rdbuf() const
 	{ return const_cast<llstdio_filebuf*>(&_M_filebuf); }
+#endif // llstream_LLFILE
 
 	/**
 	 *  @brief  Wrapper to test for an open file.

indra/newview/llviewerwearable.cpp

@@ -509,18 +509,7 @@ void LLViewerWearable::saveNewAsset() const
 	//LL_INFOS() << *this << LL_ENDL;
 
 	const std::string filename = asset_id_to_filename(mAssetID);
-	LLFILE* fp = LLFile::fopen(filename, "wb");		/* Flawfinder: ignore */
-	BOOL successful_save = FALSE;
-	if(fp && exportFile(fp))
-	{
-		successful_save = TRUE;
-	}
-	if(fp)
-	{
-		fclose(fp);
-		fp = NULL;
-	}
-	if(!successful_save)
+	if(! exportFile(filename))
 	{
 		std::string buffer = llformat("Unable to save '%s' to wearable file.", mName.c_str());
 		LL_WARNS() << buffer << LL_ENDL;