Revert "Try to compile with AppVeyor's GCC 9.1.0"

This reverts commit 749c2753e4.

src/Makefile.cfg

@@ -154,9 +154,6 @@ ifdef GCC43
 endif
 endif
  WFLAGS+=-Wsign-compare
-ifdef GCC91
- WFLAGS+=-Wno-error=address-of-packed-member
-endif
 ifdef GCC45
  WFLAGS+=-Wlogical-op
 endif
@@ -241,9 +238,6 @@ ifdef GCC80
  WFLAGS+=-Wno-error=format-overflow
  WFLAGS+=-Wno-error=stringop-truncation
  WFLAGS+=-Wno-error=stringop-overflow
-ifdef GCC91
- WFLAGS+=-Werror=-Wstringop-overflow=2
-endif
  WFLAGS+=-Wno-format-overflow
  WFLAGS+=-Wno-stringop-truncation
  WFLAGS+=-Wno-stringop-overflow

src/d_clisrv.c

@@ -1242,7 +1242,7 @@ static void SV_SendServerInfo(INT32 node, tic_t servertime)
 	netbuffer->u.serverinfo.cheatsenabled = CV_CheatsEnabled();
 	netbuffer->u.serverinfo.isdedicated = (UINT8)dedicated;
 	strncpy(netbuffer->u.serverinfo.servername, cv_servername.string,
-		MAXSERVERNAME-1);
+		MAXSERVERNAME);
 	strncpy(netbuffer->u.serverinfo.mapname, G_BuildMapName(gamemap), 7);
 
 	M_Memcpy(netbuffer->u.serverinfo.mapmd5, mapmd5, 16);

src/dehacked.c

@@ -1186,9 +1186,9 @@ static void readlevelheader(MYFILE *f, INT32 num)
 			{
 				i = get_mus(word2, true);
 				if (i && i <= 1035)
-					snprintf(mapheaderinfo[num-1]->musname, 6, "%sM", G_BuildMapName(i));
+					snprintf(mapheaderinfo[num-1]->musname, 7, "%sM", G_BuildMapName(i));
 				else if (i && i <= 1050)
-					strncpy(mapheaderinfo[num-1]->musname, compat_special_music_slots[i - 1036], 6);
+					strncpy(mapheaderinfo[num-1]->musname, compat_special_music_slots[i - 1036], 7);
 				else
 					mapheaderinfo[num-1]->musname[0] = 0; // becomes empty string
 				mapheaderinfo[num-1]->musname[6] = 0;
@@ -1213,7 +1213,7 @@ static void readlevelheader(MYFILE *f, INT32 num)
 			else if (fastcmp(word, "SKYNUM"))
 				mapheaderinfo[num-1]->skynum = (INT16)i;
 			else if (fastcmp(word, "INTERSCREEN"))
-				strncpy(mapheaderinfo[num-1]->interscreen, word2, 7);
+				strncpy(mapheaderinfo[num-1]->interscreen, word2, 8);
 			else if (fastcmp(word, "PRECUTSCENENUM"))
 				mapheaderinfo[num-1]->precutscenenum = (UINT8)i;
 			else if (fastcmp(word, "CUTSCENENUM"))
@@ -3101,7 +3101,7 @@ static void readmaincfg(MYFILE *f)
 
 				// Also save a time attack folder
 				filenamelen = strlen(gamedatafilename)-4;  // Strip off the extension
-				strncpy(timeattackfolder, gamedatafilename, min(filenamelen, sizeof (timeattackfolder)-1));
+				strncpy(timeattackfolder, gamedatafilename, min(filenamelen, sizeof (timeattackfolder)));
 				timeattackfolder[min(filenamelen, sizeof (timeattackfolder) - 1)] = '\0';
 
 				strcpy(savegamename, timeattackfolder);

src/hu_stuff.c

@@ -3072,7 +3072,7 @@ void HU_DoCEcho(const char *msg)
 {
 	I_OutputMsg("%s\n", msg); // print to log
 
-	strncpy(cechotext, msg, sizeof(cechotext)-1);
+	strncpy(cechotext, msg, sizeof(cechotext));
 	strncat(cechotext, "\\", sizeof(cechotext) - strlen(cechotext) - 1);
 	cechotext[sizeof(cechotext) - 1] = '\0';
 	cechotimer = cechoduration;

src/p_spec.c

@@ -469,7 +469,7 @@ void P_ParseAnimationDefintion(SINT8 istexture)
 		// Increase the size to make room for the new animation definition
 		maxanims++;
 		animdefs = (animdef_t *)Z_Realloc(animdefs, sizeof(animdef_t)*(maxanims + 1), PU_STATIC, NULL);
-		strncpy(animdefs[i].startname, animdefsToken, 8);
+		strncpy(animdefs[i].startname, animdefsToken, 9);
 	}
 
 	// animdefs[i].startname is now set to animdefsToken either way.

src/v_video.c

@@ -196,7 +196,7 @@ static void LoadPalette(const char *lumpname)
 const char *R_GetPalname(UINT16 num)
 {
 	static char palname[9];
-	char newpal[9] = "PLAYPAL\0";
+	char newpal[9] = "PLAYPAL";
 
 	if (num > 0 && num <= 10000)
 		snprintf(newpal, 8, "PAL%04u", num-1);