Fix warnings in Linux build

* 6 warnings are for not checking return values from system calls that indicate
errors through the return value. Fix by checking the returns properly.
* 2 warnings are for converting `NULL` to `0`; fix by using 0 where a `uint64_t`
is expected and `nullptr` otherwise.
* 2 warnings related to `memset` usage appear to be spurious, and the gcc
compiler has had similar spurious warnings before, so I'll ignore them and leave
a maintainer note.

Original warning messages below:

Core/ClientSML/src/sml_ClientAgent.cpp:1538:15: warning: ignoring return value of ‘char* getcwd(char*, size_t)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
Core/ClientSML/src/sml_ClientAgent.cpp:1708:15: warning: ignoring return value of ‘char* getcwd(char*, size_t)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
Core/SoarKernel/src/explanation_based_chunking/ebc_identity.cpp:92:94: warning: converting to non-pointer type ‘uint64_t’ {aka ‘long unsigned int’} from NULL [-Wconversion-null]
In file included from Core/SoarKernel/SoarKernel.cxx:35:
Core/SoarKernel/src/explanation_based_chunking/ebc_identity.cpp: In function ‘uint64_t get_joined_identity_chunk_inst_id(Identity*)’:
Core/SoarKernel/src/explanation_based_chunking/ebc_identity.cpp:94:94: warning: converting to non-pointer type ‘uint64_t’ {aka ‘long unsigned int’} from NULL [-Wconversion-null]
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:59:33: warning: ‘void* __builtin_memset(void*, int, long unsigned int)’ writing 16 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:59:33: warning: ‘void* __builtin_memset(void*, int, long unsigned int)’ writing 16 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
Core/CLI/src/cli_visualize.cpp:267:23: warning: ignoring return value of ‘int system(const char*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
Core/CLI/src/cli_visualize.cpp:275:23: warning: ignoring return value of ‘int system(const char*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
Core/CLI/src/cli_visualize.cpp:282:23: warning: ignoring return value of ‘int system(const char*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
UnitTests/TestHarness/TestHelpers.cpp:50:14: warning: ignoring return value of ‘int chdir(const char*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]

Core/CLI/src/cli_visualize.cpp

@@ -264,22 +264,32 @@ bool CommandLineInterface::DoVisualize(const std::string* pArg1, const std::stri
                 lSystemCommand += lFileName;
                 lSystemCommand += '.';
                 lSystemCommand += thisAgent->visualizationManager->settings->image_type->get_value();
-                system(lSystemCommand.c_str());
+                if (system(lSystemCommand.c_str()) != 0)
+                {
+                    thisAgent->visualizationManager->clear_visualization();
+                    return SetError("Error: Could not generate visualization image because `dot` command failed. Do you have GraphViz installed?!\n");
+                }
             }
             if (thisAgent->visualizationManager->settings->launch_viewer->get_value())
             {
                 lSystemCommand = "open ";
                 lSystemCommand += lFileName;
                 lSystemCommand += '.';
                 lSystemCommand += thisAgent->visualizationManager->settings->image_type->get_value();
-                system(lSystemCommand.c_str());
+                if (system(lSystemCommand.c_str()) != 0) {
+                    thisAgent->visualizationManager->clear_visualization();
+                    return SetError("Error: Could not generate visualization image because failed to open file generated by `dot` command.\n");
+                }
             }
             if (thisAgent->visualizationManager->settings->launch_editor->get_value())
             {
                 lSystemCommand = "open ";
                 lSystemCommand += lFileName;
                 lSystemCommand += ".gv";
-                system(lSystemCommand.c_str());
+                if (system(lSystemCommand.c_str()) != 0)
+                {
+                    return SetError("Error: Could not open .gv file for editing.\n");
+                }
             }
             if (thisAgent->visualizationManager->settings->print_gv->get_value())
             {

Core/ClientSML/src/sml_ClientAgent.cpp

@@ -1535,7 +1535,11 @@ bool Agent::SpawnDebugger(int port, const char* jarpath)
 #ifdef _MSC_VER
         GetCurrentDirectory(4096, buffer);
 #else
-        getcwd(buffer, 4096);
+        if (getcwd(buffer, 4096) != buffer)
+        {
+            perror("getcwd");
+            return false;
+        }
 #endif
 
         std::string debuggerPath = buffer;
@@ -1705,7 +1709,11 @@ bool Agent::SpawnDebugger(int port, const char* jarpath)
         }
 
         char buffer[4096 + 1];
-        getcwd(buffer, 4096);
+        if (getcwd(buffer, 4096) != buffer)
+        {
+            perror("getcwd");
+            return false;
+        }
 
         path += ":";
         path += buffer;

Core/SoarKernel/src/explanation_based_chunking/ebc_identity.cpp

@@ -89,7 +89,7 @@ void Identity::set_operational_cond(condition* pCond, WME_Field pField)
         joined_identity->touch();
 }
 
-uint64_t    get_joined_identity_id(Identity* pIdentity)             { if (!pIdentity) return NULL_IDENTITY_SET; else return pIdentity->get_identity(); }
-Identity*   get_joined_identity(Identity* pIdentity)                { if (!pIdentity) return NULL; else return pIdentity->joined_identity;}
-uint64_t    get_joined_identity_chunk_inst_id(Identity* pIdentity)  { if (!pIdentity) return NULL_IDENTITY_SET; else return pIdentity->get_clone_identity();}
+uint64_t    get_joined_identity_id(Identity* pIdentity)             { if (!pIdentity) return NULL_IDENTIFIER_ID; else return pIdentity->get_identity(); }
+Identity*   get_joined_identity(Identity* pIdentity)                { if (!pIdentity) return NULL_IDENTITY_SET; else return pIdentity->joined_identity;}
+uint64_t    get_joined_identity_chunk_inst_id(Identity* pIdentity)  { if (!pIdentity) return NULL_IDENTIFIER_ID; else return pIdentity->get_clone_identity();}
 

Core/SoarKernel/src/shared/constants.h

@@ -12,7 +12,8 @@
                       Explanation-Based Chunking
 ------------------------------------------------------------------------ */
 #define LITERAL_VALUE 0
-#define NULL_IDENTITY_SET NULL
+#define NULL_IDENTITY_SET nullptr
+#define NULL_IDENTIFIER_ID 0
 
 #define PE_PRODS 0
 #define IE_PRODS 1

Core/SoarKernel/src/shared/memory_manager.cpp

@@ -271,14 +271,14 @@ void* Memory_Manager::allocate_memory(size_t size, int usage_code)
     if (p == NULL)
     {
         char msg[BUFFER_MSG_SIZE];
-        SNPRINTF(msg, BUFFER_MSG_SIZE, "\nmem.c: Error:  Tried but failed to allocate %zu bytes of memory.\n", size);
+        SNPRINTF(msg, BUFFER_MSG_SIZE, "\nmemory_manager.cpp: Error:  Tried but failed to allocate %zu bytes of memory.\n", size);
         msg[BUFFER_MSG_SIZE - 1] = 0; /* ensure null termination */
         abort_with_fatal_error_noagent(msg);
     }
     if (reinterpret_cast<uintptr_t>(p) & 3)
     {
         char msg[BUFFER_MSG_SIZE];
-        strncpy(msg, "\nmem.c: Error:  Memory allocator returned an address that's not a multiple of 4.\n", BUFFER_MSG_SIZE);
+        strncpy(msg, "\nmemory_manager.cpp: Error:  Memory allocator returned an address that's not a multiple of 4.\n", BUFFER_MSG_SIZE);
         msg[BUFFER_MSG_SIZE - 1] = 0; /* ensure null termination */
         abort_with_fatal_error_noagent(msg);
     }

SConstruct

@@ -194,6 +194,7 @@ if GetOption('cc') != None:
     env.Replace(CC=GetOption('cc'))
 elif sys.platform == 'darwin':
     env.Replace(CC='clang')
+
 if GetOption('cxx') != None:
     env.Replace(CXX=GetOption('cxx'))
 elif sys.platform == 'darwin':
@@ -217,6 +218,8 @@ lnflags = []
 libs = ['Soar']
 if compiler == 'g++':
     libs += [ 'pthread', 'dl', 'm' ]
+    # causes some spurious warnings; TODO: revisit and re-enable if newer compiler version fixes that
+    cflags.append('-Wno-stringop-overflow')
     if GetOption('nosvs'):
         cflags.append('-DNO_SVS')
     if GetOption('defflags'):

UnitTests/TestHarness/TestHelpers.cpp

@@ -47,15 +47,19 @@ void setCWDToEnv()
 {
     if (getenv("LIBSOAR") != nullptr)
     {
-        chdir(getenv("LIBSOAR"));
+        if (chdir(getenv("LIBSOAR")) != 0) {
+            std::cerr << "Could not change directory to getenv(\"LIBSOAR\") (" << getenv("LIBSOAR") << ")" << std::endl;
+            perror("chdir");
+            // no further action; tests might work fine anyway if the CWD is already correct
+        }
     }
 }
 
 void printDebugInformation(std::stringstream& output, sml::Agent* agent)
 {
 	if (!agent)
 		return;
-	
+
 //	output << "============================================================" << std::endl << std::endl;
 //	output << "Debug Information" << std::endl << std::endl;
 //	output << "============================================================" << std::endl << std::endl;
@@ -94,37 +98,37 @@ namespace TestHelpers
 #ifdef __GNUG__
 
 	std::string demangle(const char* name) {
-		
+
 		int status = -1;
-		
+
 		std::unique_ptr<char, void(*)(void*)> res {
 			abi::__cxa_demangle(name, NULL, NULL, &status),
 			std::free
 		};
-		
+
 		return (status==0) ? res.get() : name ;
 	}
 
 	// VS2013 +
 #elif _MSC_VER
-	
+
 	std::string demangle(const char* name)
 	{
 		std::string result = name;
 		result = result.substr(result.find_last_of(" ")+1, std::string::npos);
-		
+
 		return result;
 	}
 
 	// Unknown
 #else
-	
+
 	// does nothing if not g++
 	std::string demangle(const char* name)
 	{
 		return name;
 	}
-	
+
 #endif
-	
+
 };