Update allowed C++ version (#7654)

* Update allowed C++ version.

* Build examples using C++11.

* Remove pre-C++11 fallback in examples code - thanks to Alex.

doc/README.modern_cpp.md

@@ -1,11 +1,12 @@
 # Modern C++ features
 
-We define here as "modern C++" features the ones introduced since C++17. These features should be used in a "controlled" form in Firebird code, as not all compilers fully support them.
+It's allowed to use in Firebird internal code C++ features up to and including C++17.
 
-Only ones mentioned in this document could be used, but as necessities appears, discussion should be started in the devel list or pull requests.
+Public files (as API headers) is limited to C++11.
+
+Exceptions to these rules should be listed below and must be agreed by the team,
+discussing in the devel list or by pull request.
 
 ## Allowed features
 
-### C++17
+### C++20
-
-- [if with init-statement](https://en.cppreference.com/w/cpp/language/if)

doc/Using_OO_API.html

@@ -1604,7 +1604,7 @@ ISomePlugin implementation</i></font></p>
 <p style="margin-bottom: 0cm"><font size="4" style="font-size: 14pt"><i>private:</i></font></p>
 <p style="margin-bottom: 0cm"><font size="4" style="font-size: 14pt"><i>IPluginConfig*
 config;</i></font></p>
-<p style="margin-bottom: 0cm"><font size="4" style="font-size: 14pt"><i>FbSampleAtomic
+<p style="margin-bottom: 0cm"><font size="4" style="font-size: 14pt"><i>std::atomic_int
 refCounter;</i></font></p>
 <p style="margin-bottom: 0cm"><font size="4" style="font-size: 14pt"><i>IReferenceCounted*
 owner;</i></font></p>

examples/dbcrypt/CryptKeyHolder.cpp

@@ -25,6 +25,7 @@
  */
 
 #include "../interfaces/ifaceExamples.h"
+#include <atomic>
 
 namespace
 {
@@ -189,7 +190,7 @@ private:
 	IPluginConfig* config;
 	ISC_UCHAR key;
 
-	FbSampleAtomic refCounter;
+	std::atomic_int refCounter;
 	IReferenceCounted* owner;
 
 	IConfigEntry* getEntry(CheckStatusWrapper* status, const char* entryName);

examples/dbcrypt/DbCrypt.cpp

@@ -25,6 +25,7 @@
  */
 
 #include "../interfaces/ifaceExamples.h"
+#include <atomic>
 
 using namespace Firebird;
 
@@ -121,7 +122,7 @@ private:
 	char savedKeyName[32];
 	ISC_UCHAR key;
 
-	FbSampleAtomic refCounter;
+	std::atomic_int refCounter;
 	IReferenceCounted* owner;
 
 	void noKeyError(CheckStatusWrapper* status);

examples/extauth/Makefile

@@ -61,7 +61,7 @@ KEYGEN_objects=$(INTERMED)/keygen.o
 TCWRAP_objects=$(INTERMED)/TcWrapper.o
 KEY_AUTH_objects=$(INTERMED)/ExtAuth.o
 
-CXXFLAGS=-std=c++17 -pthread -I$(ROOT)/include -fPIC $(TOMCRYPT_COMPILE)
+CXXFLAGS=-std=c++11 -pthread -I$(ROOT)/include -fPIC $(TOMCRYPT_COMPILE)
 LDFLAGS=-pthread -L$(LIB) -Wl,-rpath,'$$ORIGIN/../lib' $(TOMCRYPT_LINK)
 
 LINK_LIBS=-lfbclient -ltomcrypt -ltommath

examples/interfaces/05.user_metadata.cpp

@@ -31,6 +31,7 @@
  */
 
 #include "ifaceExamples.h"
+#include <atomic>
 
 static IMaster* master = fb_get_master_interface();
 
@@ -66,7 +67,7 @@ private:
 		}
 	};
 
-	FbSampleAtomic referenceCounter;
+	std::atomic_int referenceCounter;
 
 	// we are using only single field (varchar) in a sample, therefore no strong alignment requirements.
 	// In general message alignment is the maximum field alignment in that message.

examples/interfaces/08.events.cpp

@@ -26,6 +26,7 @@
  */
 
 #include "ifaceExamples.h"
+#include <atomic>
 
 #ifndef WIN32
 #include <unistd.h>
@@ -115,7 +116,7 @@ namespace
 			status.dispose();
 		}
 
-		FbSampleAtomic refCounter;
+		std::atomic_int refCounter;
 		IAttachment* attachment;
 		volatile int counter;
 		ThrowStatusWrapper status;

examples/interfaces/ifaceExamples.h

@@ -28,13 +28,6 @@
 #include <stdio.h>
 #include <string.h>
 
-#if defined(__cplusplus) && (__cplusplus >= 201103L)
-#include <atomic>
-typedef std::atomic_int FbSampleAtomic;
-#else
-typedef int FbSampleAtomic;
-#endif
-
 #include <firebird/Interface.h>
 
 using namespace Firebird;

examples/interfaces/makefile

@@ -33,7 +33,7 @@ FBCLIENT = $(FIREBIRD)/lib/libfbclient.so
 # General Compiler and linker Defines for Linux
 # ---------------------------------------------------------------------
 CXX	= c++
-CXXFLAGS= -c -Wall -g3 -std=c++17  -fno-rtti $(INCLUDE)
+CXXFLAGS= -c -Wall -g3 -std=c++11 -fno-rtti $(INCLUDE)
 RM	= rm -f
 
 #

examples/readme

@@ -173,9 +173,6 @@ Program               Description
 12.batch_isc.cpp      Working with batch interface from ISC API.
 
 
-FbSampleAtomic        typedef required in many examples.
-
-
 
 dbcrypt - a sample of XOR database encryption (do not use in production!!!)