diff --git a/hecl/blender/BlenderConnection.hpp b/hecl/blender/BlenderConnection.hpp
index f3478bdf2..8f1f2781e 100644
--- a/hecl/blender/BlenderConnection.hpp
+++ b/hecl/blender/BlenderConnection.hpp
@@ -126,6 +126,9 @@ public:
                 m_parent->m_lock = false;
             }
         }
+#if __GNUC__
+        __attribute__((__format__ (__printf__, 2, 3)))
+#endif
         void format(const char* fmt, ...)
         {
             if (!m_parent || !m_parent->m_lock)
diff --git a/hecl/driver/ToolExtract.hpp b/hecl/driver/ToolExtract.hpp
index 590f52be1..de650a0fb 100644
--- a/hecl/driver/ToolExtract.hpp
+++ b/hecl/driver/ToolExtract.hpp
@@ -218,7 +218,7 @@ public:
                 if (submessageLen)
                 {
                     if (messageLen > half-submessageLen-1)
-                        HECL::Printf(_S("%.*s... "), half-submessageLen-4, message);
+                        HECL::Printf(_S("%.*s... "), half-int(submessageLen)-4, message);
                     else
                     {
                         HECL::Printf(_S("%s"), message);
@@ -246,9 +246,9 @@ public:
                     size_t rem = blocks - filled;
                     HECL::Printf(_S("" BOLD "%3d%% ["), iFactor);
                     for (int b=0 ; b<filled ; ++b)
-                        HECL::Printf(_S("#"), message);
+                        HECL::Printf(_S("#"));
                     for (int b=0 ; b<rem ; ++b)
-                        HECL::Printf(_S("-"), message);
+                        HECL::Printf(_S("-"));
                     HECL::Printf(_S("]" NORMAL ""));
                 }
                 else
@@ -258,9 +258,9 @@ public:
                     size_t rem = blocks - filled;
                     HECL::Printf(_S("%3d%% ["), iFactor);
                     for (int b=0 ; b<filled ; ++b)
-                        HECL::Printf(_S("#"), message);
+                        HECL::Printf(_S("#"));
                     for (int b=0 ; b<rem ; ++b)
-                        HECL::Printf(_S("-"), message);
+                        HECL::Printf(_S("-"));
                     HECL::Printf(_S("]"));
                 }
 
diff --git a/hecl/include/HECL/HECL.hpp b/hecl/include/HECL/HECL.hpp
index 36d614b8d..934d4c102 100644
--- a/hecl/include/HECL/HECL.hpp
+++ b/hecl/include/HECL/HECL.hpp
@@ -231,6 +231,9 @@ static inline int Stat(const SystemChar* path, Sstat* statOut)
 #endif
 }
 
+#if __GNUC__
+__attribute__((__format__ (__printf__, 1, 2)))
+#endif
 static inline void Printf(const SystemChar* format, ...)
 {
     va_list va;
@@ -243,6 +246,9 @@ static inline void Printf(const SystemChar* format, ...)
     va_end(va);
 }
 
+#if __GNUC__
+__attribute__((__format__ (__printf__, 2, 3)))
+#endif
 static inline void FPrintf(FILE* fp, const SystemChar* format, ...)
 {
     va_list va;
@@ -255,6 +261,9 @@ static inline void FPrintf(FILE* fp, const SystemChar* format, ...)
     va_end(va);
 }
 
+#if __GNUC__
+__attribute__((__format__ (__printf__, 3, 4)))
+#endif
 static inline void SNPrintf(SystemChar* str, size_t maxlen, const SystemChar* format, ...)
 {
     va_list va;
@@ -269,6 +278,9 @@ static inline void SNPrintf(SystemChar* str, size_t maxlen, const SystemChar* fo
 
 #define FORMAT_BUF_SZ 1024
 
+#if __GNUC__
+__attribute__((__format__ (__printf__, 1, 2)))
+#endif
 static inline SystemString SysFormat(const SystemChar* format, ...)
 {
     SystemChar resultBuf[FORMAT_BUF_SZ];
@@ -283,6 +295,9 @@ static inline SystemString SysFormat(const SystemChar* format, ...)
     return SystemString(resultBuf, printSz);
 }
 
+#if __GNUC__
+__attribute__((__format__ (__printf__, 1, 2)))
+#endif
 static inline std::string Format(const char* format, ...)
 {
     char resultBuf[FORMAT_BUF_SZ];