Some GCC compilation fixes (#3114)

* Fix 6-byte multichar literals

* Add `struct` to `e_ga_class::ga_s`

* Fix remaining wrong forward declares (struct/class)

* Replace `#include <string>` with `#include <cstring>`

* Guard FLT_EPSILON define to prevent redefinition

* Add missing `#include <cstring>` for direct cstring function usage

33 files changed, 36 insertions, 21 deletions

diff --git a/include/JSystem/J3DGraphLoader/J3DMaterialFactory.h b/include/JSystem/J3DGraphLoader/J3DMaterialFactory.h
index bed19cd693..6c5f371b1d 100644
--- a/include/JSystem/J3DGraphLoader/J3DMaterialFactory.h
+++ b/include/JSystem/J3DGraphLoader/J3DMaterialFactory.h
@@ -84,7 +84,7 @@ struct J3DDisplayListInit {
 }; // size 8
 
 struct J3DTexCoord2Info;
-struct J3DCurrentMtxInfo;
+class J3DCurrentMtxInfo;
 
 /**
  * @ingroup jsystem-j3d
diff --git a/include/JSystem/J3DGraphLoader/J3DMaterialFactory_v21.h b/include/JSystem/J3DGraphLoader/J3DMaterialFactory_v21.h
index af166e1b13..e59d158959 100644
--- a/include/JSystem/J3DGraphLoader/J3DMaterialFactory_v21.h
+++ b/include/JSystem/J3DGraphLoader/J3DMaterialFactory_v21.h
@@ -7,7 +7,7 @@
 
 class J3DMaterial;
 struct J3DTexCoord2Info;
-struct J3DCurrentMtxInfo;
+class J3DCurrentMtxInfo;
 
 /**
  * @ingroup jsystem-j3d
diff --git a/include/JSystem/J3DGraphLoader/J3DModelLoader.h b/include/JSystem/J3DGraphLoader/J3DModelLoader.h
index a06260f3dc..e2569cee19 100644
--- a/include/JSystem/J3DGraphLoader/J3DModelLoader.h
+++ b/include/JSystem/J3DGraphLoader/J3DModelLoader.h
@@ -6,7 +6,7 @@
 
 class J3DModelData;
 class J3DMaterialTable;
-class J3DModelHierarchy;
+struct J3DModelHierarchy;
 
 /**
  * @ingroup jsystem-j3d
diff --git a/include/JSystem/JAudio2/JAISound.h b/include/JSystem/JAudio2/JAISound.h
index 96e6d96d9a..5e414ade24 100644
--- a/include/JSystem/JAudio2/JAISound.h
+++ b/include/JSystem/JAudio2/JAISound.h
@@ -68,7 +68,7 @@ public:
     } id_;
 };
 
-class JASTrack;
+struct JASTrack;
 
 /**
  * @ingroup jsystem-jaudio
diff --git a/include/JSystem/JAudio2/JASChannel.h b/include/JSystem/JAudio2/JASChannel.h
index 5b4a959372..8c80268d46 100644
--- a/include/JSystem/JAudio2/JASChannel.h
+++ b/include/JSystem/JAudio2/JASChannel.h
@@ -8,7 +8,7 @@
 #include "JSystem/JAudio2/JASWaveInfo.h"
 #include <dolphin/os.h>
 
-class JASDSPChannel;
+struct JASDSPChannel;
 
 namespace JASDsp {
     struct TChannel;
diff --git a/include/JSystem/JAudio2/JASCmdStack.h b/include/JSystem/JAudio2/JASCmdStack.h
index c35a1146cb..2ad327362b 100644
--- a/include/JSystem/JAudio2/JASCmdStack.h
+++ b/include/JSystem/JAudio2/JASCmdStack.h
@@ -3,7 +3,7 @@
 
 #include "JSystem/JSupport/JSUList.h"
 
-class JASTrack;
+struct JASTrack;
 
 /**
  * @ingroup jsystem-jaudio
diff --git a/include/JSystem/JAudio2/JASSeqCtrl.h b/include/JSystem/JAudio2/JASSeqCtrl.h
index 974f1c7065..d481192d6f 100644
--- a/include/JSystem/JAudio2/JASSeqCtrl.h
+++ b/include/JSystem/JAudio2/JASSeqCtrl.h
@@ -3,7 +3,7 @@
 
 #include "JSystem/JAudio2/JASSeqReader.h"
 
-class JASTrack;
+struct JASTrack;
 class JASSeqParser;
 
 /**
diff --git a/include/JSystem/JAudio2/JASWSParser.h b/include/JSystem/JAudio2/JASWSParser.h
index 000aee0069..1dc68674cf 100644
--- a/include/JSystem/JAudio2/JASWSParser.h
+++ b/include/JSystem/JAudio2/JASWSParser.h
@@ -5,8 +5,8 @@
 
 class JKRHeap;
 class JASWaveBank;
-class JASBasicWaveBank;
-class JASSimpleWaveBank;
+struct JASBasicWaveBank;
+struct JASSimpleWaveBank;
 
 /**
  * @ingroup jsystem-jaudio
diff --git a/include/JSystem/JGadget/search.h b/include/JSystem/JGadget/search.h
index bbc5c9ce6c..12507f3dc7 100644
--- a/include/JSystem/JGadget/search.h
+++ b/include/JSystem/JGadget/search.h
@@ -5,6 +5,7 @@
 #include <iterator>
 #include <functional>
 #include <algorithm>
+#include <cstring>
 
 namespace JGadget {
 namespace search {
diff --git a/include/JSystem/JGadget/std-streambuf.h b/include/JSystem/JGadget/std-streambuf.h
index d6bf291415..dae56d317c 100644
--- a/include/JSystem/JGadget/std-streambuf.h
+++ b/include/JSystem/JGadget/std-streambuf.h
@@ -2,7 +2,7 @@
 #define JGADGET_STD_STREAMBUF_H
 
 #include <dolphin/types.h>
-#include <string>
+#include <cstring>
 
 namespace JGadget {
 template <typename T>
diff --git a/include/JSystem/JGeometry.h b/include/JSystem/JGeometry.h
index 696d2f60a4..d0e7c8c03e 100644
--- a/include/JSystem/JGeometry.h
+++ b/include/JSystem/JGeometry.h
@@ -7,8 +7,10 @@
 
 #ifndef __MWERKS__
 #include <limits>
+#if !defined(FLT_EPSILON)
 #define FLT_EPSILON std::numeric_limits<float>::epsilon()
 #endif
+#endif
 
 namespace JGeometry {
 
diff --git a/include/SSystem/SComponent/c_m2d.h b/include/SSystem/SComponent/c_m2d.h
index f6fe537a76..482dcab0e3 100644
--- a/include/SSystem/SComponent/c_m2d.h
+++ b/include/SSystem/SComponent/c_m2d.h
@@ -2,7 +2,7 @@
 #define C_M2D_H
 
 
-struct cM2dGCir;
+class cM2dGCir;
 
 void cM2d_CrossCirLin(cM2dGCir&, float, float, float, float, float*, float*);
 
diff --git a/include/d/actor/d_a_e_ga.h b/include/d/actor/d_a_e_ga.h
index 1b357771c6..e690a68fc8 100644
--- a/include/d/actor/d_a_e_ga.h
+++ b/include/d/actor/d_a_e_ga.h
@@ -34,7 +34,7 @@ public:
     /* 0x0570 */ u8 prm0;
     /* 0x0571 */ u8 prm1;
     /* 0x0572 */ u8 prm2;
-    /* 0x0574 */ ga_s ga_s[256];
+    /* 0x0574 */ struct ga_s ga_s[256];
     /* 0x4D74 */ int ga_num;
     /* 0x4D78 */ u8 HIOInit;
     /* 0x4D79 */ u8 initialized;
diff --git a/include/d/actor/d_a_e_pm.h b/include/d/actor/d_a_e_pm.h
index 9077a4d56d..edec93c6a2 100644
--- a/include/d/actor/d_a_e_pm.h
+++ b/include/d/actor/d_a_e_pm.h
@@ -9,7 +9,7 @@
 #include "d/d_cc_uty.h"
 #include "d/d_msg_flow.h"
 
-class dPath;
+struct dPath;
 
 /**
  * @ingroup actors-enemies
diff --git a/include/d/actor/d_a_npc.h b/include/d/actor/d_a_npc.h
index 205a242050..ea081165be 100644
--- a/include/d/actor/d_a_npc.h
+++ b/include/d/actor/d_a_npc.h
@@ -10,6 +10,7 @@
 #include "d/d_msg_flow.h"
 #include "d/d_particle_copoly.h"
 #include "global.h"
+#include <cstring>
 
 struct daNpc_GetParam1 {  // name unknown
     /* 0x0 */ int fileIdx;
diff --git a/include/d/actor/d_a_npc_bou.h b/include/d/actor/d_a_npc_bou.h
index 9a1b460ae4..583c90ff3e 100644
--- a/include/d/actor/d_a_npc_bou.h
+++ b/include/d/actor/d_a_npc_bou.h
@@ -2,6 +2,7 @@
 #define D_A_NPC_BOU_H
 
 #include "d/actor/d_a_npc.h"
+#include <cstring>
 
 struct daNpc_Bou_HIOParam {
     /* 0x00 */ daNpcT_HIOParam common;
diff --git a/include/d/actor/d_a_npc_cdn3.h b/include/d/actor/d_a_npc_cdn3.h
index 890f362862..6a2e9d7b55 100644
--- a/include/d/actor/d_a_npc_cdn3.h
+++ b/include/d/actor/d_a_npc_cdn3.h
@@ -4,6 +4,7 @@
 #include "d/actor/d_a_npc.h"
 #include "d/actor/d_a_npc_cd2.h"
 #include "d/actor/d_a_tag_schedule.h"
+#include <cstring>
 
 /**
  * @ingroup actors-npcs
diff --git a/include/d/actor/d_a_npc_kn.h b/include/d/actor/d_a_npc_kn.h
index fe30a4769f..a14a89aefe 100644
--- a/include/d/actor/d_a_npc_kn.h
+++ b/include/d/actor/d_a_npc_kn.h
@@ -2,6 +2,7 @@
 #define D_A_NPC_KN_H
 
 #include "d/actor/d_a_npc.h"
+#include <cstring>
 
 struct daNpc_Kn_HIOParam {
     /* 0x00 */ daNpcT_HIOParam common;
diff --git a/include/d/actor/d_a_npc_kolin.h b/include/d/actor/d_a_npc_kolin.h
index 314a29541b..b6fded937b 100644
--- a/include/d/actor/d_a_npc_kolin.h
+++ b/include/d/actor/d_a_npc_kolin.h
@@ -2,6 +2,7 @@
 #define D_A_NPC_KOLIN_H
 
 #include "d/actor/d_a_npc.h"
+#include <cstring>
 
 struct daNpc_Kolin_HIOParam {
     /* 0x00 */ daNpcT_HIOParam common;
diff --git a/include/d/actor/d_a_npc_the.h b/include/d/actor/d_a_npc_the.h
index 6e9a24d42b..bc78a93925 100644
--- a/include/d/actor/d_a_npc_the.h
+++ b/include/d/actor/d_a_npc_the.h
@@ -2,6 +2,7 @@
 #define D_A_NPC_THE_H
 
 #include "d/actor/d_a_npc4.h"
+#include <cstring>
 
 struct daNpcThe_HIOParam {
     /* 0x00 */ daNpcF_HIOParam common;
diff --git a/include/d/actor/d_a_obj_cblock.h b/include/d/actor/d_a_obj_cblock.h
index 1a7119a9aa..04881776ec 100644
--- a/include/d/actor/d_a_obj_cblock.h
+++ b/include/d/actor/d_a_obj_cblock.h
@@ -5,7 +5,7 @@
 #include "d/d_cc_d.h"
 #include "f_op/f_op_actor_mng.h"
 
-class dPath;
+struct dPath;
 
 /**
  * @ingroup actors-objects
diff --git a/include/d/actor/d_a_passer_mng.h b/include/d/actor/d_a_passer_mng.h
index f0ee36903f..aa2a55c00f 100644
--- a/include/d/actor/d_a_passer_mng.h
+++ b/include/d/actor/d_a_passer_mng.h
@@ -5,7 +5,7 @@
 #include "d/d_kankyo.h"
 #include "f_op/f_op_actor_mng.h"
 
-class dPath;
+struct dPath;
 
 /**
  * @ingroup actors-unsorted
diff --git a/include/d/d_bg_s_cap_poly.h b/include/d/d_bg_s_cap_poly.h
index 0cda04c739..ca4a38542c 100644
--- a/include/d/d_bg_s_cap_poly.h
+++ b/include/d/d_bg_s_cap_poly.h
@@ -4,7 +4,7 @@
 #include "d/d_bg_s_chk.h"
 #include "SSystem/SComponent/c_m3d_g_aab.h"
 
-struct dBgS_CaptPoly;
+class dBgS_CaptPoly;
 
 typedef void (*CaptPolyCallback)(dBgS_CaptPoly&, cBgD_Vtx_t*, u16, u16, u16, cM3dGPla*);
 
diff --git a/include/d/d_bg_w.h b/include/d/d_bg_w.h
index fa4ba70105..f7f38688f7 100644
--- a/include/d/d_bg_w.h
+++ b/include/d/d_bg_w.h
@@ -11,7 +11,7 @@ class cBgS_GrpPassChk;
 class cBgS_PolyPassChk;
 class fopAc_ac_c;
 struct cBgD_Vtx_t;
-struct dBgS_CaptPoly;
+class dBgS_CaptPoly;
 
 class cBgW_TriElm {
 public:
diff --git a/include/d/d_bg_w_base.h b/include/d/d_bg_w_base.h
index 0a05467820..089af244b8 100644
--- a/include/d/d_bg_w_base.h
+++ b/include/d/d_bg_w_base.h
@@ -11,7 +11,7 @@ class cBgS_GndChk;
 class cBgS_LinChk;
 class cBgS_ShdwDraw;
 class dBgS_Acch;
-struct dBgS_CaptPoly;
+class dBgS_CaptPoly;
 class dBgS_RoofChk;
 class dBgS_SphChk;
 class dBgS_SplGrpChk;
diff --git a/include/d/d_bg_w_kcol.h b/include/d/d_bg_w_kcol.h
index 36e2f9d970..7bb96ccbd4 100644
--- a/include/d/d_bg_w_kcol.h
+++ b/include/d/d_bg_w_kcol.h
@@ -9,8 +9,8 @@
 
 class cBgS_GrpPassChk;
 class cBgS_PolyPassChk;
-struct dBgPc;
-struct dBgS_CaptPoly;
+class dBgPc;
+class dBgS_CaptPoly;
 
 struct KC_PrismData {
     /* 0x0 */ f32 height;
diff --git a/include/d/d_com_inf_game.h b/include/d/d_com_inf_game.h
index 25f48c5fd6..c4278cb3cb 100644
--- a/include/d/d_com_inf_game.h
+++ b/include/d/d_com_inf_game.h
@@ -15,6 +15,7 @@
 #include "global.h"
 #include "m_Do/m_Do_controller_pad.h"
 #include "m_Do/m_Do_graphic.h"
+#include <cstring>
 
 enum dComIfG_ButtonStatus {
     /* 0x00 */ BUTTON_STATUS_NONE,
diff --git a/include/d/d_debug_camera.h b/include/d/d_debug_camera.h
index d5cd7403ac..2292f46859 100644
--- a/include/d/d_debug_camera.h
+++ b/include/d/d_debug_camera.h
@@ -3,6 +3,7 @@
 
 #include "d/d_camera.h"
 #include "JSystem/JHostIO/JORFile.h"
+#include <cstring>
 
 enum dDbgCam_KeyAction {
     /* | */ dDbgCam_KeyAction_FIXEDFRM,
diff --git a/include/d/d_map.h b/include/d/d_map.h
index bbd21787ca..5718e331b2 100644
--- a/include/d/d_map.h
+++ b/include/d/d_map.h
@@ -3,6 +3,7 @@
 
 #include "d/d_map_path_dmap.h"
 #include "JSystem/JHostIO/JORReflexible.h"
+#include <cstring>
 
 struct dMap_HIO_prm_other_s {
     /* 0x00 */ u8 field_0x0;
diff --git a/include/d/d_menu_fmap_map.h b/include/d/d_menu_fmap_map.h
index b5b6f7e8d1..b77e43ba70 100644
--- a/include/d/d_menu_fmap_map.h
+++ b/include/d/d_menu_fmap_map.h
@@ -3,6 +3,7 @@
 
 #include "SSystem/SComponent/c_counter.h"
 #include <dolphin/types.h>
+#include <cstring>
 #include "d/d_menu_fmap.h"
 #include "d/d_map.h"
 #include "d/d_map_path.h"
diff --git a/include/d/d_msg_object.h b/include/d/d_msg_object.h
index ef7135f09d..2ef3f0ad69 100644
--- a/include/d/d_msg_object.h
+++ b/include/d/d_msg_object.h
@@ -4,6 +4,7 @@
 #include "JSystem/JMessage/control.h"
 #include "d/d_com_inf_game.h"
 #include "f_op/f_op_msg.h"
+#include <cstring>
 
 class COutFont_c;
 class J2DTextBox;
diff --git a/include/d/d_name.h b/include/d/d_name.h
index 16ff3414f6..0d877e6b09 100644
--- a/include/d/d_name.h
+++ b/include/d/d_name.h
@@ -2,6 +2,7 @@
 #define D_D_NAME_H
 
 #include "d/d_select_cursor.h"
+#include <cstring>
 
 class CPaneMgr;
 class CPaneMgrAlpha;
diff --git a/include/m_Do/m_Do_hostIO.h b/include/m_Do/m_Do_hostIO.h
index 4542ff4ab9..fa4eb8b1af 100644
--- a/include/m_Do/m_Do_hostIO.h
+++ b/include/m_Do/m_Do_hostIO.h
@@ -2,7 +2,7 @@
 #define M_DO_M_DO_HOSTIO_H
 
 #include "JSystem/JHostIO/JORReflexible.h"
-#include <string>
+#include <cstring>
 
 class mDoHIO_child_c {
 public: