diff --git a/db/drivers/ogr/describe.c b/db/drivers/ogr/describe.c
index 8c2688575b0..bf1ce160a30 100644
--- a/db/drivers/ogr/describe.c
+++ b/db/drivers/ogr/describe.c
@@ -162,8 +162,8 @@ int describe_table(OGRLayerH hLayer, dbTable ** table, cursor * c)
     }
 
     for (i = 0; i < ncols; i++, col++) {
-        int sqlType;
-        int size, precision, scale;
+        int sqlType = DB_SQL_TYPE_UNKNOWN;
+        int size = 0, precision = 0, scale;
 
         hFieldDefn = OGR_FD_GetFieldDefn(hFeatureDefn, i);
         ogrType = OGR_Fld_GetType(hFieldDefn);
diff --git a/display/d.vect.thematic/main.c b/display/d.vect.thematic/main.c
index 21062d35d7a..1d8336aee4e 100644
--- a/display/d.vect.thematic/main.c
+++ b/display/d.vect.thematic/main.c
@@ -66,7 +66,7 @@ int main(int argc, char **argv)
     int *cats, ncat, nrec, ctype;
     struct Map_info Map;
     struct field_info *fi;
-    dbDriver *driver;
+    dbDriver *driver = NULL;
     dbHandle handle;
     dbCatValArray cvarr;
     struct Cell_head window;
diff --git a/display/d.vect/opt.c b/display/d.vect/opt.c
index a58886936ae..fcb9b02d7fe 100644
--- a/display/d.vect/opt.c
+++ b/display/d.vect/opt.c
@@ -109,7 +109,7 @@ void options_to_lattr(LATTR *lattr, const char *layer,
 
 int option_to_color(struct color_rgb *color, const char *color_val)
 {
-    int has_color, ret;
+    int has_color = 0, ret;
     int r, g, b;
     
     ret = G_str_to_color(color_val, &r, &g, &b);
diff --git a/imagery/i.eb.soilheatflux/g0.c b/imagery/i.eb.soilheatflux/g0.c
index 6c4571f89b2..c43ba256231 100644
--- a/imagery/i.eb.soilheatflux/g0.c
+++ b/imagery/i.eb.soilheatflux/g0.c
@@ -6,7 +6,7 @@ double g_0(double bbalb, double ndvi, double tempk, double rnet,
            double time, int roerink)
 {
     double a, b, result;
-    double r0_coef;
+    double r0_coef = 1.1;
 
     if (time <= 9.0 || time > 15.0)
         r0_coef = 1.1;
diff --git a/lib/imagery/iscatt_structs.c b/lib/imagery/iscatt_structs.c
index 638f84d4423..d4d8117718d 100644
--- a/lib/imagery/iscatt_structs.c
+++ b/lib/imagery/iscatt_structs.c
@@ -154,7 +154,7 @@ void I_sc_free_cats(struct scCats *cats)
  */
 int I_sc_add_cat(struct scCats *cats)
 {
-    int i_scatt, i_cat_id, cat_id;
+    int i_scatt, i_cat_id, cat_id = 0;
     int n_a_cats = cats->n_a_cats;
 
     if (cats->n_a_cats >= cats->n_cats)
diff --git a/lib/raster3d/getblock.c b/lib/raster3d/getblock.c
index 884c6d03d5b..2e03a92a9ec 100644
--- a/lib/raster3d/getblock.c
+++ b/lib/raster3d/getblock.c
@@ -12,7 +12,7 @@ void
 Rast3d_get_block_nocache(RASTER3D_Map * map, int x0, int y0, int z0, int nx,
                          int ny, int nz, void *block, int type)
 {
-    void *tile;
+    void *tile = NULL;
     int tileX0, tileY0, tileZ0, tileOffsX0, tileOffsY0, tileOffsZ0;
     int tileX1, tileY1, tileZ1, tileOffsX1, tileOffsY1, tileOffsZ1;
     int tx, ty, tz, dx, dy, dz, x, y, z, rows, cols, depths;
diff --git a/lib/vector/Vlib/build_pg.c b/lib/vector/Vlib/build_pg.c
index 965c95798d7..9a00c89095b 100644
--- a/lib/vector/Vlib/build_pg.c
+++ b/lib/vector/Vlib/build_pg.c
@@ -142,7 +142,7 @@ int Vect_build_pg(struct Map_info *Map, int build)
  */
 int build_topo(struct Map_info *Map, int build)
 {
-    int line, type, s, n_nodes;
+    int line, type, s, n_nodes = 0;
     int area, nareas, isle, nisles;
     int face[2];
     char stmt[DB_SQL_MAX];
diff --git a/raster/r.buffer/main.c b/raster/r.buffer/main.c
index 28aa87ab08e..e481aabe7c6 100644
--- a/raster/r.buffer/main.c
+++ b/raster/r.buffer/main.c
@@ -45,7 +45,7 @@ int main(int argc, char *argv[])
     struct Distance *pd;
     const char *input, *output, *mapset;
     char **zone_list;
-    double to_meters;
+    double to_meters = 1.0;
     const char *units;
     int offset;
     int count;
diff --git a/raster/r.fill.stats/main.c b/raster/r.fill.stats/main.c
index 1f5a7a734ca..4339e42c4b1 100644
--- a/raster/r.fill.stats/main.c
+++ b/raster/r.fill.stats/main.c
@@ -1073,8 +1073,8 @@ int main(int argc, char *argv[])
             }
         }
     }
-    char *data_type_string_in;
-    char *data_type_string_out;
+    char *data_type_string_in = NULL;
+    char *data_type_string_out = NULL;
 
     if (IN_TYPE == CELL_TYPE) {
         data_type_string_in = "integer";
diff --git a/raster/r.resamp.rst/main.c b/raster/r.resamp.rst/main.c
index d50e3b69df4..1f7ab01d4cd 100644
--- a/raster/r.resamp.rst/main.c
+++ b/raster/r.resamp.rst/main.c
@@ -126,7 +126,7 @@ int main(int argc, char *argv[])
 {
     int m1;
     struct FPRange range;
-    DCELL cellmin, cellmax;
+    DCELL cellmin = 0.0, cellmax;
     FCELL *cellrow, fcellmin;
 
     struct GModule *module;
diff --git a/raster3d/r3.in.bin/main.c b/raster3d/r3.in.bin/main.c
index 9fc9e043753..ee5e2e8f6c3 100644
--- a/raster3d/r3.in.bin/main.c
+++ b/raster3d/r3.in.bin/main.c
@@ -252,7 +252,7 @@ int main(int argc, char *argv[])
     int is_integer;
     int is_signed;
     int bytes;
-    int order;
+    int order = 0;
     int byte_swap;
     RASTER_MAP_TYPE map_type;
     off_t file_size;
diff --git a/raster3d/r3.in.v5d/v5d.c b/raster3d/r3.in.v5d/v5d.c
index 515960403eb..5e2e2fcf43d 100644
--- a/raster3d/r3.in.v5d/v5d.c
+++ b/raster3d/r3.in.v5d/v5d.c
@@ -2029,7 +2029,7 @@ v5dstruct *v5dOpenFile(const char *filename, v5dstruct * v)
 int v5dReadCompressedGrid(v5dstruct * v, int time, int var,
                           float *ga, float *gb, void *compdata)
 {
-    int pos, n, k;
+    int pos, n, k = 0;
 
     if (time < 0 || time >= v->NumTimes) {
         printf("Error in v5dReadCompressedGrid: bad timestep argument (%d)\n",
@@ -2097,7 +2097,7 @@ int v5dReadGrid(v5dstruct * v, int time, int var, float data[])
 {
     float ga[MAXLEVELS], gb[MAXLEVELS];
     void *compdata;
-    int bytes;
+    int bytes = 0;
 
     if (time < 0 || time >= v->NumTimes) {
         printf("Error in v5dReadGrid: bad timestep argument (%d)\n", time);
@@ -2490,7 +2490,7 @@ int v5dWriteGrid(v5dstruct * v, int time, int var, const float data[])
 {
     float ga[MAXLEVELS], gb[MAXLEVELS];
     void *compdata;
-    int n, bytes;
+    int n, bytes = 0;
     float min, max;
 
     if (v->Mode != 'w') {
diff --git a/raster3d/r3.out.bin/main.c b/raster3d/r3.out.bin/main.c
index c80e1f48f10..ef863bee19f 100644
--- a/raster3d/r3.out.bin/main.c
+++ b/raster3d/r3.out.bin/main.c
@@ -208,7 +208,7 @@ int main(int argc, char *argv[])
     char *outfile;
     double null_val;
     int do_stdout;
-    int order;
+    int order = 0;
     int swap_flag;
     int bytes;
     int as_integer = 0;
diff --git a/raster3d/r3.out.v5d/v5d.c b/raster3d/r3.out.v5d/v5d.c
index 4ba3327c5b4..460fd991fba 100644
--- a/raster3d/r3.out.v5d/v5d.c
+++ b/raster3d/r3.out.v5d/v5d.c
@@ -2027,7 +2027,7 @@ v5dstruct *v5dOpenFile(const char *filename, v5dstruct * v)
 int v5dReadCompressedGrid(v5dstruct * v, int time, int var,
                           float *ga, float *gb, void *compdata)
 {
-    int n, k;
+    int n, k = 0;
     off_t pos;
 
     if (time < 0 || time >= v->NumTimes) {
@@ -2096,7 +2096,7 @@ int v5dReadGrid(v5dstruct * v, int time, int var, float data[])
 {
     float ga[MAXLEVELS], gb[MAXLEVELS];
     void *compdata;
-    int bytes;
+    int bytes = 0;
 
     if (time < 0 || time >= v->NumTimes) {
         printf("Error in v5dReadGrid: bad timestep argument (%d)\n", time);
@@ -2491,7 +2491,7 @@ int v5dWriteGrid(v5dstruct * v, int time, int var, const float data[])
 {
     float ga[MAXLEVELS], gb[MAXLEVELS];
     void *compdata;
-    int n, bytes;
+    int n, bytes = 0;
     float min, max;
 
     if (v->Mode != 'w') {
diff --git a/vector/v.normal/main.c b/vector/v.normal/main.c
index 160eee044fb..d9f9fcb2072 100644
--- a/vector/v.normal/main.c
+++ b/vector/v.normal/main.c
@@ -153,7 +153,7 @@ int main(int argc, char **argv)
     nsites = 0;
     for (line = 1; line <= nlines; line++) {
         int type, cat, ret, cval;
-        double dval;
+        double dval = 0.0;
 
         G_debug(3, "line = %d", line);
 
diff --git a/vector/v.proj/main.c b/vector/v.proj/main.c
index 82c0d38b624..2061d126ed2 100644
--- a/vector/v.proj/main.c
+++ b/vector/v.proj/main.c
@@ -50,7 +50,7 @@ int main(int argc, char *argv[])
 #ifdef HAVE_PROJ_H
     struct Option *pipeline;    /* name of custom PROJ pipeline */
 #endif
-    struct Key_Value *in_proj_keys, *in_unit_keys;
+    struct Key_Value *in_proj_keys = NULL, *in_unit_keys = NULL;
     struct Key_Value *out_proj_keys, *out_unit_keys;
     struct line_pnts *Points, *Points2;
     struct line_cats *Cats;
diff --git a/vector/v.sample/main.c b/vector/v.sample/main.c
index 6702ffdbc4c..f09a1c45008 100644
--- a/vector/v.sample/main.c
+++ b/vector/v.sample/main.c
@@ -205,7 +205,7 @@ int main(int argc, char **argv)
     nlines = Vect_get_num_lines(&In);
 
     for (line = 1; line <= nlines; line++) {
-        int type, cat, ret, cval;
+        int type, cat = -1, ret, cval;
         double dval;
 
         G_debug(3, "line = %d", line);
diff --git a/vector/v.to.rast3/main.c b/vector/v.to.rast3/main.c
index 0a117af8cfd..05383064bdc 100644
--- a/vector/v.to.rast3/main.c
+++ b/vector/v.to.rast3/main.c
@@ -114,7 +114,7 @@ int main(int argc, char *argv[])
 
     nlines = Vect_get_num_lines(&Map);
     for (line = 1; line <= nlines; line++) {
-        int type, cat, depth, row, col, ret;
+        int type, cat, depth, row, col, ret = DB_FAILED;
         double value;
 
         G_percent(line, nlines, 2);