diff --git a/lib/cairodriver/draw_bitmap.c b/lib/cairodriver/draw_bitmap.c
index 25f21ddf231..f9948f9172a 100644
--- a/lib/cairodriver/draw_bitmap.c
+++ b/lib/cairodriver/draw_bitmap.c
@@ -38,7 +38,7 @@ void Cairo_Bitmap(int ncols, int nrows, int threshold, const unsigned char *buf)
 #define MULTIPLE 4
     stride = (ncols + (MULTIPLE - 1)) / MULTIPLE * MULTIPLE;
 #endif
-    data = malloc(stride * nrows);
+    data = malloc((size_t)stride * nrows);
     surf = cairo_image_surface_create_for_data(data, CAIRO_FORMAT_A8, ncols,
                                                nrows, stride);
 
diff --git a/lib/cairodriver/graph.c b/lib/cairodriver/graph.c
index dadd40a176a..0bd9b356f6c 100644
--- a/lib/cairodriver/graph.c
+++ b/lib/cairodriver/graph.c
@@ -390,7 +390,8 @@ static int ends_with(const char *string, const char *suffix)
 static void map_file(void)
 {
 #ifndef _WIN32
-    size_t size = HEADER_SIZE + ca.width * ca.height * sizeof(unsigned int);
+    size_t size =
+        HEADER_SIZE + (size_t)ca.width * ca.height * sizeof(unsigned int);
     void *ptr;
     int fd;
 
diff --git a/lib/external/ccmath/hmgen.c b/lib/external/ccmath/hmgen.c
index 2ebd566c0c8..8d2859e16b8 100644
--- a/lib/external/ccmath/hmgen.c
+++ b/lib/external/ccmath/hmgen.c
@@ -17,7 +17,7 @@ void hmgen(Cpx *h, double *ev, Cpx *u, int n)
 
     double e;
 
-    v = (Cpx *)calloc(n * n, sizeof(Cpx));
+    v = (Cpx *)calloc((size_t)n * n, sizeof(Cpx));
     cmcpy(v, u, n * n);
     hconj(v, n);
     for (i = 0, p = v; i < n; ++i) {
diff --git a/lib/external/ccmath/unitary.c b/lib/external/ccmath/unitary.c
index 2258a64692f..ec02fe1f76d 100644
--- a/lib/external/ccmath/unitary.c
+++ b/lib/external/ccmath/unitary.c
@@ -24,7 +24,7 @@ void unitary(Cpx *u, int n)
     double *g, *q, a;
 
     m = n * n;
-    g = (double *)calloc(n * n, sizeof(double));
+    g = (double *)calloc((size_t)n * n, sizeof(double));
     v = (Cpx *)calloc(m + n, sizeof(Cpx));
     e = v + m;
     h.re = 1.;
diff --git a/lib/gmath/del2g.c b/lib/gmath/del2g.c
index a0e64846669..d1d02202c97 100644
--- a/lib/gmath/del2g.c
+++ b/lib/gmath/del2g.c
@@ -46,8 +46,8 @@ int del2g(double *img[2], int size, double w)
     G_message(_("    taking FFT of image..."));
     fft(FORWARD, img, size * size, size, size);
 
-    g[0] = (double *)G_malloc(size * size * sizeof(double));
-    g[1] = (double *)G_malloc(size * size * sizeof(double));
+    g[0] = (double *)G_malloc((size_t)size * size * sizeof(double));
+    g[1] = (double *)G_malloc((size_t)size * size * sizeof(double));
 
     G_message(_("    computing del**2 g..."));
     getg(w, g, size);
diff --git a/lib/gmath/getg.c b/lib/gmath/getg.c
index 58cca3d0403..bf2c0cc6cd3 100644
--- a/lib/gmath/getg.c
+++ b/lib/gmath/getg.c
@@ -17,7 +17,7 @@ int getg(double w, double *g[2], int size)
     long i, j, totsize, n, g_row;
     float rsq, sigma, two_ssq, val, sum = 0.0;
 
-    totsize = size * size;
+    totsize = (long)size * size;
     n = size / 2;
     for (i = 0; i < totsize; i++) {
         *(g[0] + i) = 0.0;
diff --git a/lib/linkm/new.c b/lib/linkm/new.c
index 3d6059b33a1..d6505c1f54a 100644
--- a/lib/linkm/new.c
+++ b/lib/linkm/new.c
@@ -32,8 +32,8 @@ VOID_T *link_new(struct link_head *Head)
 
         /*DEBUG fprintf (stderr, "Mallocing another chunk: %d\n",
          * Head->max_ptr); */
-        if (NULL ==
-            (tmp = (VOID_T *)malloc(Head->chunk_size * Head->unit_size))) {
+        if (NULL == (tmp = (VOID_T *)malloc((size_t)Head->chunk_size *
+                                            Head->unit_size))) {
             if (Head->exit_flag)
                 link_out_of_memory();
             return NULL;
diff --git a/lib/pngdriver/graph_close.c b/lib/pngdriver/graph_close.c
index e6dba3f6166..f446ee6c497 100644
--- a/lib/pngdriver/graph_close.c
+++ b/lib/pngdriver/graph_close.c
@@ -27,7 +27,8 @@
 
 static void unmap_file(void)
 {
-    size_t size = HEADER_SIZE + png.width * png.height * sizeof(unsigned int);
+    size_t size =
+        HEADER_SIZE + (size_t)png.width * png.height * sizeof(unsigned int);
     void *ptr = (char *)png.grid - HEADER_SIZE;
 
     if (!png.mapped)
diff --git a/lib/pngdriver/graph_set.c b/lib/pngdriver/graph_set.c
index ab0bacbff38..c448bd62bff 100644
--- a/lib/pngdriver/graph_set.c
+++ b/lib/pngdriver/graph_set.c
@@ -33,7 +33,8 @@ struct png_state png;
 
 static void map_file(void)
 {
-    size_t size = HEADER_SIZE + png.width * png.height * sizeof(unsigned int);
+    size_t size =
+        HEADER_SIZE + (size_t)png.width * png.height * sizeof(unsigned int);
     void *ptr;
     int fd;
 
@@ -158,7 +159,8 @@ int PNG_Graph_set(void)
         map_file();
 
     if (!png.mapped)
-        png.grid = G_malloc(png.width * png.height * sizeof(unsigned int));
+        png.grid =
+            G_malloc((size_t)png.width * png.height * sizeof(unsigned int));
 
     if (!do_read) {
         PNG_Erase();
diff --git a/lib/raster/get_row.c b/lib/raster/get_row.c
index 066b3c9a3e8..5fddb183900 100644
--- a/lib/raster/get_row.c
+++ b/lib/raster/get_row.c
@@ -90,7 +90,7 @@ static void read_data_fp_compressed(int fd, int row, unsigned char *data_buf,
     off_t t1 = fcb->row_ptr[row];
     off_t t2 = fcb->row_ptr[row + 1];
     size_t readamount = t2 - t1;
-    size_t bufsize = fcb->cellhd.cols * fcb->nbytes;
+    size_t bufsize = (size_t)fcb->cellhd.cols * fcb->nbytes;
     int ret;
 
     if (lseek(fcb->data_fd, t1, SEEK_SET) == -1)
@@ -188,7 +188,7 @@ static void read_data_uncompressed(int fd, int row, unsigned char *data_buf,
                                    int *nbytes)
 {
     struct fileinfo *fcb = &R__.fileinfo[fd];
-    ssize_t bufsize = fcb->cellhd.cols * fcb->nbytes;
+    ssize_t bufsize = (ssize_t)fcb->cellhd.cols * fcb->nbytes;
 
     *nbytes = fcb->nbytes;
 
diff --git a/lib/raster/put_row.c b/lib/raster/put_row.c
index b3c870045d0..19c31158ede 100644
--- a/lib/raster/put_row.c
+++ b/lib/raster/put_row.c
@@ -115,7 +115,7 @@ void Rast_put_d_row(int fd, const DCELL *buf)
 static void write_data(int fd, int row, unsigned char *buf, int n)
 {
     struct fileinfo *fcb = &R__.fileinfo[fd];
-    ssize_t nwrite = fcb->nbytes * n;
+    ssize_t nwrite = (ssize_t)fcb->nbytes * n;
 
     if (write(fcb->data_fd, buf, nwrite) != nwrite)
         G_fatal_error(
@@ -411,7 +411,7 @@ static void put_data(int fd, char *null_buf, const CELL *cell, int row, int n,
         G_free(compressed_buf);
     }
     else {
-        nwrite = fcb->nbytes * n;
+        nwrite = (ssize_t)fcb->nbytes * n;
 
         if (write(fcb->data_fd, work_buf, nwrite) != nwrite)
             G_fatal_error(
diff --git a/lib/raster3d/cache.c b/lib/raster3d/cache.c
index aa28845f546..4a4b3ee7edc 100644
--- a/lib/raster3d/cache.c
+++ b/lib/raster3d/cache.c
@@ -75,7 +75,7 @@ static int cacheWrite_readFun(int tileIndex, void *tileBuf, void *closure)
 
     pos = -pos - 2; /* pos is shifted by 2 to avoid 0 and -1 */
 
-    nBytes = map->tileSize * map->numLengthIntern;
+    nBytes = (size_t)map->tileSize * map->numLengthIntern;
     offs = pos * (nBytes + sizeof(int));
 
     /* seek tile and read it into buffer */
@@ -149,7 +149,7 @@ static int cacheWrite_writeFun(int tileIndex, const void *tileBuf,
         return 1;
 
     map->cachePosLast++;
-    nBytes = map->tileSize * map->numLengthIntern;
+    nBytes = (size_t)map->tileSize * map->numLengthIntern;
     offs = map->cachePosLast * (nBytes + sizeof(int));
 
     if (lseek(map->cacheFD, offs, SEEK_SET) == -1) {
@@ -299,7 +299,7 @@ int Rast3d_flush_all_tiles(RASTER3D_Map *map)
 
     /* first flush all the tiles which are in the file cache */
 
-    nBytes = map->tileSize * map->numLengthIntern;
+    nBytes = (size_t)map->tileSize * map->numLengthIntern;
 
     while (map->cachePosLast >= 0) {
         offs = map->cachePosLast * (nBytes + sizeof(int)) + nBytes;
diff --git a/lib/raster3d/misc.c b/lib/raster3d/misc.c
index 599d409e1e3..de69881c9bc 100644
--- a/lib/raster3d/misc.c
+++ b/lib/raster3d/misc.c
@@ -67,7 +67,7 @@ void Rast3d_copy_values(const void *src, int offsSrc, int typeSrc, void *dst,
     src = G_incr_void_ptr(src, eltLength * offsSrc);
     dst = G_incr_void_ptr(dst, eltLength * offsDst);
 
-    memcpy(dst, src, nElts * eltLength);
+    memcpy(dst, src, (size_t)nElts * eltLength);
 }
 
 /*---------------------------------------------------------------------------*/
diff --git a/lib/raster3d/tilewrite.c b/lib/raster3d/tilewrite.c
index 6239a6a9852..6f2c646c5d0 100644
--- a/lib/raster3d/tilewrite.c
+++ b/lib/raster3d/tilewrite.c
@@ -73,8 +73,8 @@ static int Rast3d_tile2xdrTile(RASTER3D_Map *map, const void *tile, int rows,
 
 static int Rast3d_writeTileUncompressed(RASTER3D_Map *map, int nofNum)
 {
-    if (write(map->data_fd, xdr, map->numLengthExtern * nofNum) !=
-        map->numLengthExtern * nofNum) {
+    if (write(map->data_fd, xdr, (size_t)map->numLengthExtern * nofNum) !=
+        (ssize_t)map->numLengthExtern * nofNum) {
         Rast3d_error("Rast3d_writeTileUncompressed: can't write file.");
         return 0;
     }
diff --git a/lib/raster3d/volume.c b/lib/raster3d/volume.c
index 491fae84c6b..b33337ecb7e 100644
--- a/lib/raster3d/volume.c
+++ b/lib/raster3d/volume.c
@@ -202,7 +202,8 @@ void Rast3d_make_aligned_volume_file(void *map, const char *fileName,
     int x, y, z, eltLength;
     RASTER3D_Region region;
 
-    volumeBuf = Rast3d_malloc(nx * ny * nz * sizeof(Rast3d_get_file_type()));
+    volumeBuf =
+        Rast3d_malloc((size_t)nx * ny * nz * sizeof(Rast3d_get_file_type()));
     if (volumeBuf == NULL)
         Rast3d_fatal_error(
             "Rast3d_make_aligned_volume_file: error in Rast3d_malloc");
diff --git a/lib/segment/address.c b/lib/segment/address.c
index 7562467f5b0..a917d1bf40f 100644
--- a/lib/segment/address.c
+++ b/lib/segment/address.c
@@ -85,7 +85,7 @@ int seg_address_slow(const SEGMENT *SEG, off_t row, off_t col, int *n,
     /* for simple arrays */
     else {
         *n = col / SEG->scols;
-        *index = col - *n * SEG->scols;
+        *index = col - (off_t)*n * SEG->scols;
     }
     *index *= SEG->len;
 
diff --git a/lib/vector/diglib/allocation.c b/lib/vector/diglib/allocation.c
index d2fb62a36d3..b5f6cfaaa7b 100644
--- a/lib/vector/diglib/allocation.c
+++ b/lib/vector/diglib/allocation.c
@@ -151,7 +151,7 @@ void *dig__frealloc(void *oldptr, int nelem, int elsize, int oldnelem)
         register char *b;
         register size_t n;
 
-        n = oldnelem * elsize;
+        n = (size_t)oldnelem * elsize;
         a = ptr;
         b = oldptr;
         while (n--)