diff --git a/src/p_lx_elf.cpp b/src/p_lx_elf.cpp
index 81821ab1..a7015625 100644
--- a/src/p_lx_elf.cpp
+++ b/src/p_lx_elf.cpp
@@ -319,8 +319,8 @@ PackLinuxElf32ppc::buildLinuxLoader(
 
     linker->addSection("ELFPPC32", proto, szproto);
 
-    addLoader("ELFPPC32", 0);
-    addLoader("FOLDEXEC", 0);
+    addLoader("ELFPPC32", NULL);
+    addLoader("FOLDEXEC", NULL);
     return getLoaderSize();
 }
 
@@ -373,8 +373,8 @@ PackLinuxElf64amd::buildLinuxLoader(
 
     linker->addSection("ELF64AMD", proto, szproto);
 
-    addLoader("ELF64AMD", 0);
-    addLoader("FOLDEXEC", 0);
+    addLoader("ELF64AMD", NULL);
+    addLoader("FOLDEXEC", NULL);
     return getLoaderSize();
 }
 
diff --git a/src/p_lx_exc.cpp b/src/p_lx_exc.cpp
index 4a918b3c..647af6b1 100644
--- a/src/p_lx_exc.cpp
+++ b/src/p_lx_exc.cpp
@@ -291,71 +291,71 @@ PackLinuxI386::buildLinuxLoader(
             // compressed data
         b_len + ph.c_len );
             // entry to stub
-    addLoader("LEXEC000", 0);
+    addLoader("LEXEC000", NULL);
 
     if (ft->id) {
         if (ph.format==UPX_F_LINUX_ELF_i386) { // decompr, unfilter are separate
-            addLoader("LXUNF000", 0);
-            addLoader("LXUNF002", 0);
+            addLoader("LXUNF000", NULL);
+            addLoader("LXUNF002", NULL);
                 if (0x80==(ft->id & 0xF0)) {
                     if (256==n_mru) {
-                        addLoader("MRUBYTE0", 0);
+                        addLoader("MRUBYTE0", NULL);
                     }
                     else if (n_mru) {
-                        addLoader("LXMRU005", 0);
+                        addLoader("LXMRU005", NULL);
                     }
                     if (n_mru) {
-                        addLoader("LXMRU006", 0);
+                        addLoader("LXMRU006", NULL);
                     }
                     else {
-                        addLoader("LXMRU007", 0);
+                        addLoader("LXMRU007", NULL);
                     }
             }
             else if (0x40==(ft->id & 0xF0)) {
-                addLoader("LXUNF008", 0);
+                addLoader("LXUNF008", NULL);
             }
-            addLoader("LXUNF010", 0);
+            addLoader("LXUNF010", NULL);
         }
         if (n_mru) {
-            addLoader("LEXEC009", 0);
+            addLoader("LEXEC009", NULL);
         }
     }
-    addLoader("LEXEC010", 0);
-    addLoader(getDecompressor(), 0);
-    addLoader("LEXEC015", 0);
+    addLoader("LEXEC010", NULL);
+    addLoader(getDecompressor(), NULL);
+    addLoader("LEXEC015", NULL);
     if (ft->id) {
         if (ph.format==UPX_F_LINUX_ELF_i386) {  // decompr, unfilter are separate
             if (0x80!=(ft->id & 0xF0)) {
-                addLoader("LXUNF042", 0);
+                addLoader("LXUNF042", NULL);
             }
         }
         else {  // decompr, unfilter not separate
             if (0x80==(ft->id & 0xF0)) {
-                addLoader("LEXEC110", 0);
+                addLoader("LEXEC110", NULL);
                 if (n_mru) {
-                    addLoader("LEXEC100", 0);
+                    addLoader("LEXEC100", NULL);
                 }
                 // bug in APP: jmp and label must be in same .asx/.asy
-                addLoader("LEXEC016", 0);
+                addLoader("LEXEC016", NULL);
             }
         }
         addFilter32(ft->id);
         if (ph.format==UPX_F_LINUX_ELF_i386) { // decompr, unfilter are separate
             if (0x80==(ft->id & 0xF0)) {
                 if (0==n_mru) {
-                    addLoader("LXMRU058", 0);
+                    addLoader("LXMRU058", NULL);
                 }
             }
-            addLoader("LXUNF035", 0);
+            addLoader("LXUNF035", NULL);
         }
         else {  // decompr always unfilters
-            addLoader("LEXEC017", 0);
+            addLoader("LEXEC017", NULL);
         }
     }
 
-    addLoader("IDENTSTR", 0);
-    addLoader("LEXEC020", 0);
-    addLoader("FOLDEXEC", 0);
+    addLoader("IDENTSTR", NULL);
+    addLoader("LEXEC020", NULL);
+    addLoader("FOLDEXEC", NULL);
 
     char *ptr_cto = (char *)const_cast<unsigned char *>(getLoader());
     int sz_cto = getLoaderSize();
diff --git a/src/p_lx_interp.cpp b/src/p_lx_interp.cpp
index e683164f..978a258a 100644
--- a/src/p_lx_interp.cpp
+++ b/src/p_lx_interp.cpp
@@ -147,38 +147,38 @@ void PackLinuxI386interp::pack3(OutputFile *fo, Filter &/*ft*/)
         initLoader(linux_i386pti_loader, sizeof(linux_i386pti_loader));
         linker->addSection("FOLDEXEC", linux_i386pti_fold, sizeof(linux_i386pti_fold));
 
-        addLoader("LXPTI000", 0);
+        addLoader("LXPTI000", NULL);
 
-        addLoader("LXPTI040", 0);
-        ph.method = M_NRV2B_LE32; addLoader(getDecompressor(), 0);
-        addLoader("LXPTI090", 0);
+        addLoader("LXPTI040", NULL);
+        ph.method = M_NRV2B_LE32; addLoader(getDecompressor(), NULL);
+        addLoader("LXPTI090", NULL);
 
-        addLoader("LXPTI041", 0);
-        ph.method = M_NRV2D_LE32; addLoader(getDecompressor(), 0);
-        addLoader("LXPTI090", 0);
+        addLoader("LXPTI041", NULL);
+        ph.method = M_NRV2D_LE32; addLoader(getDecompressor(), NULL);
+        addLoader("LXPTI090", NULL);
 
-        addLoader("LXPTI042", 0);
-        ph.method = M_NRV2E_LE32; addLoader(getDecompressor(), 0);
-        addLoader("LXPTI090", 0);
+        addLoader("LXPTI042", NULL);
+        ph.method = M_NRV2E_LE32; addLoader(getDecompressor(), NULL);
+        addLoader("LXPTI090", NULL);
 
-        addLoader("LXPTI043", 0);
-        ph.method = M_CL1B_LE32;  addLoader(getDecompressor(), 0);
-        addLoader("LXPTI090", 0);
+        addLoader("LXPTI043", NULL);
+        ph.method = M_CL1B_LE32;  addLoader(getDecompressor(), NULL);
+        addLoader("LXPTI090", NULL);
 
-        addLoader("LXPTI091", 0);
+        addLoader("LXPTI091", NULL);
 
-        addLoader("LXPTI140", 0);
+        addLoader("LXPTI140", NULL);
 
-        addLoader("LXUNF002,LXUNF008,LXUNF010", 0);
+        addLoader("LXUNF002,LXUNF008,LXUNF010", NULL);
         addFilter32(0x46);
-        addLoader("LXUNF042,LXUNF035", 0);
+        addLoader("LXUNF042,LXUNF035", NULL);
 
-        addLoader("LXUNF002,LXUNF008,LXUNF010", 0);
+        addLoader("LXUNF002,LXUNF008,LXUNF010", NULL);
         addFilter32(0x49);
-        addLoader("LXUNF042,LXUNF035", 0);
+        addLoader("LXUNF042,LXUNF035", NULL);
 
-        addLoader("LXPTI200", 0);
-        addLoader("FOLDEXEC", 0);
+        addLoader("LXPTI200", NULL);
+        addLoader("FOLDEXEC", NULL);
         upx_byte const *p = getLoader();
         lsize = getLoaderSize();
         updateLoader(fo);
diff --git a/src/p_mach.cpp b/src/p_mach.cpp
index 641151da..01693b98 100644
--- a/src/p_mach.cpp
+++ b/src/p_mach.cpp
@@ -106,8 +106,8 @@ PackMachPPC32::buildMachLoader(
 
     linker->addSection("MACOS000", proto, szproto);
 
-    addLoader("MACOS000", 0);
-    addLoader("FOLDEXEC", 0);
+    addLoader("MACOS000", NULL);
+    addLoader("FOLDEXEC", NULL);
     return getLoaderSize();
 }
 
diff --git a/src/packer.h b/src/packer.h
index b2de61ca..af25b95e 100644
--- a/src/packer.h
+++ b/src/packer.h
@@ -210,7 +210,11 @@ protected:
     virtual const upx_byte *getLoader() const;
     virtual int getLoaderSize() const;
     virtual void initLoader(const void *pdata, int plen, int pinfo=-1, int small=-1);
+#if 1 && (ACC_CC_GNUC >= 0x040100) && (ACC_OS_POSIX_LINUX)
+    virtual void __acc_cdecl_va addLoader(const char *s, ...) __attribute__((__sentinel__));
+#else
     virtual void __acc_cdecl_va addLoader(const char *s, ...);
+#endif
     virtual int getLoaderSection(const char *name, int *slen=NULL) const;
     virtual int getLoaderSectionStart(const char *name, int *slen=NULL) const;
     virtual const char *getDecompressor() const;
diff --git a/src/packerf.cpp b/src/packerf.cpp
index 1385eacb..1b461bb8 100644
--- a/src/packerf.cpp
+++ b/src/packerf.cpp
@@ -139,15 +139,15 @@ void Packer::addFilter32(int filter_id)
                         );
             }
             else if (0x40==(0xF0 & filter_id)) {
-                addLoader("CKLLTR00", 0);
+                addLoader("CKLLTR00", NULL);
                 if (9<=(0xf & filter_id)) {
-                    addLoader("CKLLTR10", 0);
+                    addLoader("CKLLTR10", NULL);
                 }
-                addLoader("CKLLTR20", 0);
+                addLoader("CKLLTR20", NULL);
                 if (9<=(0xf & filter_id)) {
-                    addLoader("CKLLTR30", 0);
+                    addLoader("CKLLTR30", NULL);
                 }
-                addLoader("CKLLTR40", 0);
+                addLoader("CKLLTR40", NULL);
             }
         }
         else
@@ -170,187 +170,187 @@ void Packer::addFilter32(int filter_id)
         unsigned const f_jcc2 = f80_jcc2(filter_id);
 
         if (NOFILT!=f_jcc2) {
-                addLoader("LXJCC010", 0);
+                addLoader("LXJCC010", NULL);
                 if (n_mru) {
-                    addLoader("LXMRU045", 0);
+                    addLoader("LXMRU045", NULL);
                 }
                 else {
-                    addLoader("LXMRU046", 0);
+                    addLoader("LXMRU046", NULL);
                 }
                 if (0==n_mru || MRUFLT!=f_jcc2) {
-                    addLoader("LXJCC020", 0);
+                    addLoader("LXJCC020", NULL);
                 }
                 else { // 0!=n_mru
-                    addLoader("LXJCC021", 0);
+                    addLoader("LXJCC021", NULL);
                 }
                 if (NOFILT!=f_jcc2) {
-                    addLoader("LXJCC023", 0);
+                    addLoader("LXJCC023", NULL);
                 }
         }
-        addLoader("LXUNF037", 0);
+        addLoader("LXUNF037", NULL);
         if (x386) {
             if (n_mru) {
-                addLoader("LXUNF386", 0);
+                addLoader("LXUNF386", NULL);
             }
-            addLoader("LXUNF387", 0);
+            addLoader("LXUNF387", NULL);
             if (n_mru) {
-                addLoader("LXUNF388", 0);
+                addLoader("LXUNF388", NULL);
             }
         }
         else {
-            addLoader("LXUNF486", 0);
+            addLoader("LXUNF486", NULL);
             if (n_mru) {
-                addLoader("LXUNF487", 0);
+                addLoader("LXUNF487", NULL);
             }
         }
         if (n_mru) {
-            addLoader("LXMRU065", 0);
+            addLoader("LXMRU065", NULL);
             if (256==n_mru) {
-                addLoader("MRUBYTE3", 0);
+                addLoader("MRUBYTE3", NULL);
             }
             else {
-                addLoader("MRUARB30", 0);
+                addLoader("MRUARB30", NULL);
                 if (mrupwr2) {
-                    addLoader("MRUBITS3", 0);
+                    addLoader("MRUBITS3", NULL);
                 }
                 else {
-                    addLoader("MRUARB40", 0);
+                    addLoader("MRUARB40", NULL);
                 }
             }
-            addLoader("LXMRU070", 0);
+            addLoader("LXMRU070", NULL);
             if (256==n_mru) {
-                addLoader("MRUBYTE4", 0);
+                addLoader("MRUBYTE4", NULL);
             }
             else if (mrupwr2) {
-                addLoader("MRUBITS4", 0);
+                addLoader("MRUBITS4", NULL);
             }
             else {
-                addLoader("MRUARB50", 0);
+                addLoader("MRUARB50", NULL);
             }
-            addLoader("LXMRU080", 0);
+            addLoader("LXMRU080", NULL);
             if (256==n_mru) {
-                addLoader("MRUBYTE5", 0);
+                addLoader("MRUBYTE5", NULL);
             }
             else {
-                addLoader("MRUARB60", 0);
+                addLoader("MRUARB60", NULL);
                 if (mrupwr2) {
-                    addLoader("MRUBITS5", 0);
+                    addLoader("MRUBITS5", NULL);
                 }
                 else {
-                    addLoader("MRUARB70", 0);
+                    addLoader("MRUARB70", NULL);
                 }
             }
-            addLoader("LXMRU090", 0);
+            addLoader("LXMRU090", NULL);
             if (256==n_mru) {
-                addLoader("MRUBYTE6", 0);
+                addLoader("MRUBYTE6", NULL);
             }
             else {
-                addLoader("MRUARB80", 0);
+                addLoader("MRUARB80", NULL);
                 if (mrupwr2) {
-                        addLoader("MRUBITS6", 0);
+                        addLoader("MRUBITS6", NULL);
                 }
                 else {
-                    addLoader("MRUARB90", 0);
+                    addLoader("MRUARB90", NULL);
                 }
             }
-            addLoader("LXMRU100", 0);
+            addLoader("LXMRU100", NULL);
         }
-        addLoader("LXUNF040", 0);
+        addLoader("LXUNF040", NULL);
         if (n_mru) {
-            addLoader("LXMRU110", 0);
+            addLoader("LXMRU110", NULL);
         }
         else {
-            addLoader("LXMRU111", 0);
+            addLoader("LXMRU111", NULL);
         }
-        addLoader("LXUNF041", 0);
-        addLoader("LXUNF042", 0);
+        addLoader("LXUNF041", NULL);
+        addLoader("LXUNF042", NULL);
         if (n_mru) {
-            addLoader("LXMRU010", 0);
+            addLoader("LXMRU010", NULL);
             if (NOFILT!=f_jmp1 && NOFILT==f_call) {
-                addLoader("LXJMPA00", 0);
+                addLoader("LXJMPA00", NULL);
             }
             else {
-                addLoader("LXCALLB0", 0);
+                addLoader("LXCALLB0", NULL);
             }
-            addLoader("LXUNF021", 0);
+            addLoader("LXUNF021", NULL);
         }
         else {
-            addLoader("LXMRU022", 0);
+            addLoader("LXMRU022", NULL);
             if (NOFILT!=f_jmp1 && NOFILT==f_call) {
-                addLoader("LXJMPA01", 0);
+                addLoader("LXJMPA01", NULL);
             }
             else {
-                addLoader("LXCALLB1", 0);
+                addLoader("LXCALLB1", NULL);
             }
         }
         if (n_mru) {
             if (256!=n_mru && mrupwr2) {
-                addLoader("MRUBITS1", 0);
+                addLoader("MRUBITS1", NULL);
             }
-            addLoader("LXMRU030", 0);
+            addLoader("LXMRU030", NULL);
             if (256==n_mru) {
-                addLoader("MRUBYTE1", 0);
+                addLoader("MRUBYTE1", NULL);
             }
             else {
-                addLoader("MRUARB10", 0);
+                addLoader("MRUARB10", NULL);
             }
-            addLoader("LXMRU040", 0);
+            addLoader("LXMRU040", NULL);
         }
 
-        addLoader("LXUNF030", 0);
+        addLoader("LXUNF030", NULL);
         if (NOFILT!=f_jcc2) {
-            addLoader("LXJCC000", 0);
+            addLoader("LXJCC000", NULL);
         }
         if (NOFILT!=f_call || NOFILT!=f_jmp1) { // at least one is filtered
             // shift opcode origin to zero
             if (0==n_mru) {
-                addLoader("LXCJ0MRU", 0);
+                addLoader("LXCJ0MRU", NULL);
             }
             else {
-                addLoader("LXCJ1MRU", 0);
+                addLoader("LXCJ1MRU", NULL);
             }
 
             // determine if in range
             if ((NOFILT!=f_call) && (NOFILT!=f_jmp1)) { // unfilter both
-                addLoader("LXCALJMP", 0);
+                addLoader("LXCALJMP", NULL);
             }
             if ((NOFILT==f_call) ^  (NOFILT==f_jmp1)) { // unfilter just one
                 if (0==n_mru) {
-                    addLoader("LXCALL00", 0);
+                    addLoader("LXCALL00", NULL);
                 }
                 else {
-                    addLoader("LXCALL01", 0);
+                    addLoader("LXCALL01", NULL);
                 }
             }
 
             // determine if mru applies
             if (0==n_mru || ! ((FNOMRU==f_call) || (FNOMRU==f_jmp1)) ) {
-                addLoader("LXCJ2MRU", 0);  // no mru, or no exceptions
+                addLoader("LXCJ2MRU", NULL);  // no mru, or no exceptions
             }
             else {  // mru on one, but not the other
-                addLoader("LXCJ4MRU", 0);
+                addLoader("LXCJ4MRU", NULL);
                 if (MRUFLT==f_jmp1) { // JMP only
-                    addLoader("LXCJ6MRU", 0);
+                    addLoader("LXCJ6MRU", NULL);
                 } else
                 if (MRUFLT==f_call) { // CALL only
-                    addLoader("LXCJ7MRU", 0);
+                    addLoader("LXCJ7MRU", NULL);
                 }
-                addLoader("LXCJ8MRU", 0);
+                addLoader("LXCJ8MRU", NULL);
             }
         }
-        addLoader("LXUNF034", 0);
+        addLoader("LXUNF034", NULL);
         if (n_mru) {
-            addLoader("LXMRU055", 0);
+            addLoader("LXMRU055", NULL);
             if (256==n_mru) {
-                addLoader("MRUBYTE2", 0);
+                addLoader("MRUBYTE2", NULL);
             }
             else if (mrupwr2) {
-                addLoader("MRUBITS2", 0);
+                addLoader("MRUBITS2", NULL);
             }
             else if (n_mru) {
-                addLoader("MRUARB20", 0);
+                addLoader("MRUARB20", NULL);
             }
-            addLoader("LXMRU057", 0);
+            addLoader("LXMRU057", NULL);
         }
     }
 }