diff --git a/benchmarks/benchmark_assimp/main.cpp b/benchmarks/benchmark_assimp/main.cpp
index 599caab..c28bf24 100644
--- a/benchmarks/benchmark_assimp/main.cpp
+++ b/benchmarks/benchmark_assimp/main.cpp
@@ -127,7 +127,7 @@ static void allocate_stl_scene(aiScene* pScene)
 }
 
 static void func_ascii_begin_solid(
-        void* cookie, size_t stream_size, const char* solid_name)
+        void* cookie, gmio_streamsize_t stream_size, const char* solid_name)
 {
     aiSceneHelper* helper = (aiSceneHelper*)cookie;
     helper->hasToCountTriangle = 1; // true
diff --git a/benchmarks/benchmark_gmio/main.c b/benchmarks/benchmark_gmio/main.c
index 436757e..1d88b37 100644
--- a/benchmarks/benchmark_gmio/main.c
+++ b/benchmarks/benchmark_gmio/main.c
@@ -77,7 +77,7 @@ typedef struct stl_readwrite_conv
 } stl_readwrite_conv_t;
 
 static void readwrite_ascii_begin_solid(
-        void* cookie, size_t stream_size, const char* solid_name)
+        void* cookie, gmio_streamsize_t stream_size, const char* solid_name)
 {
     stl_readwrite_conv_t* rw_conv = (stl_readwrite_conv_t*)cookie;
     gmio_stream_t* stream = &rw_conv->trsf.stream;
diff --git a/src/gmio_core/internal/helper_stream.h b/src/gmio_core/internal/helper_stream.h
index 3e27610..8bcd931 100644
--- a/src/gmio_core/internal/helper_stream.h
+++ b/src/gmio_core/internal/helper_stream.h
@@ -53,7 +53,7 @@ GMIO_INLINE size_t gmio_stream_write(
 }
 
 /*! Safe and convenient function for gmio_stream::func_size() */
-GMIO_INLINE size_t gmio_stream_size(gmio_stream_t* stream)
+GMIO_INLINE gmio_streamsize_t gmio_stream_size(gmio_stream_t* stream)
 {
     if (stream != NULL && stream->func_size != NULL)
         return stream->func_size(stream->cookie);
diff --git a/src/gmio_core/internal/safe_cast.h b/src/gmio_core/internal/safe_cast.h
index 5eea114..30906ec 100644
--- a/src/gmio_core/internal/safe_cast.h
+++ b/src/gmio_core/internal/safe_cast.h
@@ -17,17 +17,35 @@
 #define GMIO_INTERNAL_SAFE_CAST_H
 
 #include "../global.h"
+#include "../stream.h"
 
 #include <stddef.h>
 
+
 /*! Returns \p val safely casted to unsigned 32b integer */
 GMIO_INLINE uint32_t gmio_size_to_uint32(size_t val)
 {
 #if GMIO_TARGET_ARCH_BIT_SIZE > 32
+    /* TODO : eliminate branch */
     return val > 0xFFFFFFFF ? 0xFFFFFFFF : (uint32_t)val;
 #else
     return val;
 #endif
 }
 
+#define GMIO_MAX_SIZET  ((size_t)-1)
+
+/*! Returns \p val safely casted to \c size_t */
+GMIO_INLINE size_t gmio_streamsize_to_size(gmio_streamsize_t val)
+{
+#if GMIO_TARGET_ARCH_BIT_SIZE < 64 \
+    && defined(GMIO_HAVE_INT64_TYPE)
+    /* TODO : eliminate branch */
+    const uint64_t uval = val;
+    return uval > GMIO_MAX_SIZET ? GMIO_MAX_SIZET : (size_t)uval;
+#else
+    return (size_t)val;
+#endif
+}
+
 #endif /* GMIO_INTERNAL_SAFE_CAST_H */
diff --git a/src/gmio_core/stream.c b/src/gmio_core/stream.c
index 86df0d7..102c01c 100644
--- a/src/gmio_core/stream.c
+++ b/src/gmio_core/stream.c
@@ -73,7 +73,7 @@ static size_t gmio_stream_stdio_write(
     return fwrite(ptr, item_size, item_count, (FILE*)cookie);
 }
 
-static size_t gmio_stream_stdio_size(void* cookie)
+static gmio_streamsize_t gmio_stream_stdio_size(void* cookie)
 {
     FILE* file = (FILE*)cookie;
 
diff --git a/src/gmio_core/stream.h b/src/gmio_core/stream.h
index caf35a7..38be1f2 100644
--- a/src/gmio_core/stream.h
+++ b/src/gmio_core/stream.h
@@ -27,6 +27,14 @@
 #include "stream_pos.h"
 #include <stdio.h>
 
+#ifdef GMIO_HAVE_INT64_TYPE
+typedef int64_t gmio_streamsize_t;
+typedef int64_t gmio_streamoffset_t;
+#else
+typedef long gmio_streamsize_t;
+typedef long gmio_streamoffset_t;
+#endif
+
 /*! Stream that can get input from an arbitrary data source or can write
  *  output to an arbitrary data sink.
  *
@@ -93,7 +101,7 @@ struct gmio_stream
     size_t (*func_write)(void* cookie, const void* ptr, size_t size, size_t count);
 
     /*! Pointer on a function that returns the size(in bytes) of the stream */
-    size_t (*func_size)(void* cookie);
+    gmio_streamsize_t (*func_size)(void* cookie);
 
     /*! Pointer on a function that retrieves the current position in the stream
      *
diff --git a/src/gmio_core/stream_pos.h b/src/gmio_core/stream_pos.h
index 2128cf3..85f3191 100644
--- a/src/gmio_core/stream_pos.h
+++ b/src/gmio_core/stream_pos.h
@@ -26,7 +26,7 @@
 #include "global.h"
 
 /*! Size of the byte array gmio_stream_pos::cookie */
-enum { GMIO_STREAM_POS_COOKIE_SIZE = 32 }; /* 32 bytes */
+enum { GMIO_STREAM_POS_COOKIE_SIZE = 32 /* bytes */ };
 
 /*! Specifies a position within a stream
  *
diff --git a/src/gmio_stl/internal/helper_stl_mesh_creator.h b/src/gmio_stl/internal/helper_stl_mesh_creator.h
index 3dae7a8..ead3fd6 100644
--- a/src/gmio_stl/internal/helper_stl_mesh_creator.h
+++ b/src/gmio_stl/internal/helper_stl_mesh_creator.h
@@ -22,7 +22,7 @@
  *  gmio_stl_mesh_creator::func_ascii_begin_solid() */
 GMIO_INLINE void gmio_stl_mesh_creator_ascii_begin_solid(
         gmio_stl_mesh_creator_t* creator,
-        size_t stream_size,
+        gmio_streamsize_t stream_size,
         const char* solid_name)
 {
     if (creator != NULL && creator->func_ascii_begin_solid != NULL) {
diff --git a/src/gmio_stl/internal/stl_funptr_typedefs.h b/src/gmio_stl/internal/stl_funptr_typedefs.h
index a212921..8a52495 100644
--- a/src/gmio_stl/internal/stl_funptr_typedefs.h
+++ b/src/gmio_stl/internal/stl_funptr_typedefs.h
@@ -30,7 +30,7 @@ typedef void (*gmio_stl_mesh_func_get_triangle_t)(
 
 /* gmio_stl_mesh_creator */
 typedef void (*gmio_stl_mesh_creator_func_ascii_begin_solid_t)(
-        void*, size_t, const char*);
+        void*, gmio_streamsize_t, const char*);
 typedef void (*gmio_stl_mesh_creator_func_binary_begin_solid_t)(
         void*, uint32_t, const gmio_stlb_header_t*);
 typedef void (*gmio_stl_mesh_creator_func_add_triangle_t)(
diff --git a/src/gmio_stl/stl_format.c b/src/gmio_stl/stl_format.c
index c0a8cc6..213881a 100644
--- a/src/gmio_stl/stl_format.c
+++ b/src/gmio_stl/stl_format.c
@@ -49,7 +49,7 @@ gmio_stl_format_t gmio_stl_get_format(gmio_stream_t *stream)
 
     /* Binary STL ? */
     if (read_size >= (GMIO_STLB_HEADER_SIZE + 4)) {
-        const size_t stream_size = gmio_stream_size(stream);
+        const gmio_streamsize_t stream_size = gmio_stream_size(stream);
 
         /* Try with little-endian format */
         uint32_t facet_count =
diff --git a/src/gmio_stl/stl_mesh_creator.h b/src/gmio_stl/stl_mesh_creator.h
index 55570cc..ccb3f5f 100644
--- a/src/gmio_stl/stl_mesh_creator.h
+++ b/src/gmio_stl/stl_mesh_creator.h
@@ -26,6 +26,7 @@
 #include "stl_global.h"
 #include "stl_triangle.h"
 #include "stlb_header.h"
+#include "../gmio_core/stream.h"
 
 #include <stddef.h>
 
@@ -48,7 +49,7 @@ struct gmio_stl_mesh_creator
      *  stream
      */
     void (*func_ascii_begin_solid)(
-            void* cookie, size_t stream_size, const char* solid_name);
+            void* cookie, gmio_streamsize_t stream_size, const char* solid_name);
 
     /*! Pointer on a function that handles declaration of a mesh with
      *  \p tri_count number of triangles
diff --git a/src/gmio_stl/stla_read.c b/src/gmio_stl/stla_read.c
index 16e643a..99b7a5e 100644
--- a/src/gmio_stl/stla_read.c
+++ b/src/gmio_stl/stla_read.c
@@ -134,9 +134,9 @@ typedef struct
     /* Copy of gmio_stla_read() corresponding argument */
     gmio_transfer_t* transfer;
     /* Cache for gmio_stream_size(&transfer->stream) */
-    size_t stream_size;
+    gmio_streamsize_t stream_size;
     /* Offset (in bytes) from beginning of stream : current position */
-    size_t stream_offset;
+    gmio_streamoffset_t stream_offset;
     /* Cache for gmio_transfer::func_is_stop_requested() */
     gmio_bool_t is_stop_requested;
 } gmio_string_stream_fwd_iterator_cookie_t;
diff --git a/src/gmio_support/stream_cpp.h b/src/gmio_support/stream_cpp.h
index 1a55a91..0182b03 100644
--- a/src/gmio_support/stream_cpp.h
+++ b/src/gmio_support/stream_cpp.h
@@ -20,6 +20,10 @@
  *  @{
  */
 
+#ifndef __cplusplus
+#  error C++ compiler required
+#endif
+
 #ifndef GMIO_SUPPORT_STREAM_CPP_H
 #define GMIO_SUPPORT_STREAM_CPP_H
 
@@ -68,7 +72,7 @@ size_t istream_cpp_read(
 {
     STREAM* s = static_cast<STREAM*>(cookie);
     s->read(static_cast<char*>(ptr), item_size * item_count);
-    return s->gcount() / item_size;
+    return static_cast<size_t>(s->gcount() / item_size);
 }
 
 template<typename STREAM>
@@ -82,7 +86,7 @@ size_t ostream_cpp_write(
 }
 
 template<typename STREAM>
-size_t istream_cpp_size(void* cookie)
+gmio_streamsize_t istream_cpp_size(void* cookie)
 {
     STREAM* s = static_cast<STREAM*>(cookie);
     std::streampos pos = s->tellg();
@@ -95,7 +99,7 @@ size_t istream_cpp_size(void* cookie)
 }
 
 template<typename STREAM>
-size_t ostream_cpp_size(void* cookie)
+gmio_streamsize_t ostream_cpp_size(void* cookie)
 {
     STREAM* s = static_cast<STREAM*>(cookie);
     std::streampos pos = s->tellp();
diff --git a/src/gmio_support/stream_qt.cpp b/src/gmio_support/stream_qt.cpp
index 44de056..8408ebe 100644
--- a/src/gmio_support/stream_qt.cpp
+++ b/src/gmio_support/stream_qt.cpp
@@ -46,7 +46,7 @@ static size_t gmio_stream_qiodevice_read(
 {
     QIODevice* device = static_cast<QIODevice*>(cookie);
     const qint64 c = device->read(static_cast<char*>(ptr), item_size * item_count);
-    return c / item_size;
+    return static_cast<size_t>(c / item_size);
 }
 
 static size_t gmio_stream_qiodevice_write(
@@ -55,10 +55,10 @@ static size_t gmio_stream_qiodevice_write(
     QIODevice* device = static_cast<QIODevice*>(cookie);
     const qint64 c = device->write(
                 static_cast<const char*>(ptr), item_size * item_count);
-    return c / item_size;
+    return static_cast<size_t>(c / item_size);
 }
 
-static size_t gmio_stream_qiodevice_size(void* cookie)
+static gmio_streamsize_t gmio_stream_qiodevice_size(void* cookie)
 {
     QIODevice* device = static_cast<QIODevice*>(cookie);
     return device->size();
diff --git a/src/gmio_support/stream_qt.h b/src/gmio_support/stream_qt.h
index f649240..15804a9 100644
--- a/src/gmio_support/stream_qt.h
+++ b/src/gmio_support/stream_qt.h
@@ -20,6 +20,10 @@
  *  @{
  */
 
+#ifndef __cplusplus
+#  error C++ compiler required
+#endif
+
 #ifndef GMIO_SUPPORT_STREAM_QT_H
 #define GMIO_SUPPORT_STREAM_QT_H
 
diff --git a/tests/stl_utils.c b/tests/stl_utils.c
index 362e1da..89db978 100644
--- a/tests/stl_utils.c
+++ b/tests/stl_utils.c
@@ -44,7 +44,7 @@ gmio_stl_triangle_array_t gmio_stl_triangle_array_malloc(size_t tri_count)
 }
 
 static void gmio_stl_data__ascii_begin_solid(
-        void* cookie, size_t stream_size, const char* solid_name)
+        void* cookie, gmio_streamsize_t stream_size, const char* solid_name)
 {
     gmio_stl_data_t* data = (gmio_stl_data_t*)cookie;
 
@@ -59,7 +59,8 @@ static void gmio_stl_data__ascii_begin_solid(
      * for each face */
     {
         const size_t facet_size = 200;
-        const size_t facet_count = GMIO_MAX(1, stream_size / facet_size);
+        const size_t facet_count =
+                gmio_streamsize_to_size(GMIO_MAX(1, stream_size / facet_size));
         data->tri_array = gmio_stl_triangle_array_malloc(facet_count);
     }
 }
diff --git a/tests/stream_buffer.c b/tests/stream_buffer.c
index de7cb2b..95d75b8 100644
--- a/tests/stream_buffer.c
+++ b/tests/stream_buffer.c
@@ -78,7 +78,7 @@ static size_t gmio_stream_buffer_write(
     }
 }
 
-static size_t gmio_stream_buffer_size(void* cookie)
+static gmio_streamsize_t gmio_stream_buffer_size(void* cookie)
 {
     const gmio_stream_buffer_t* buff = (const gmio_stream_buffer_t*)cookie;
     return buff->len;
diff --git a/tests/test_core_internal.c b/tests/test_core_internal.c
index 17d4870..4e130d3 100644
--- a/tests/test_core_internal.c
+++ b/tests/test_core_internal.c
@@ -132,6 +132,18 @@ const char* test_internal__safe_cast()
     UTEST_ASSERT(gmio_size_to_uint32(0xFFFFFFFF) == 0xFFFFFFFF);
     UTEST_ASSERT(gmio_size_to_uint32(100) == 100);
 #endif
+
+    UTEST_ASSERT(gmio_streamsize_to_size(-1) == ((size_t)-1));
+#ifdef GMIO_HAVE_INT64_TYPE
+#  if GMIO_TARGET_ARCH_BIT_SIZE < 64
+    const gmio_streamsize_t overMaxSizet =
+            ((gmio_streamsize_t)GMIO_MAX_SIZET) + 1;
+    UTEST_ASSERT(gmio_streamsize_to_size(overMaxSizet) == GMIO_MAX_SIZET);
+#  endif
+    UTEST_ASSERT(gmio_streamsize_to_size(GMIO_MAX_SIZET) == GMIO_MAX_SIZET);
+    UTEST_ASSERT(gmio_streamsize_to_size(150) == 150);
+#endif
+
     return NULL;
 }
 
diff --git a/tests/test_stl_io.c b/tests/test_stl_io.c
index 16ca0b8..df6c40f 100644
--- a/tests/test_stl_io.c
+++ b/tests/test_stl_io.c
@@ -36,7 +36,7 @@ struct stl_testcase_result
 typedef struct stl_testcase_result stl_testcase_result_t;
 
 void stl_testcase_result__ascii_begin_solid(
-        void* cookie, size_t stream_size, const char* solid_name)
+        void* cookie, gmio_streamsize_t stream_size, const char* solid_name)
 {
     stl_testcase_result_t* res = (stl_testcase_result_t*)cookie;
     GMIO_UNUSED(stream_size);