some cares about compiler warnings

src/sage/algebras/fusion_rings/fast_parallel_fmats_methods.pyx

@@ -316,7 +316,7 @@ cdef get_reduced_pentagons(factory, tuple mp_params):
     # Pre-compute common parameters for speed
     cdef tuple basis = tuple(factory._FR.basis())
     # Handle both cyclotomic and orthogonal solution method
-    cdef bint must_zip_up
+    cdef bint must_zip_up = False
     for k, v in factory._fvars.items():
         must_zip_up = isinstance(v, tuple)
         break

src/sage/algebras/letterplace/free_algebra_letterplace.pyx

@@ -810,7 +810,7 @@ cdef class FreeAlgebra_letterplace(Parent):
         """
         if not D:
             return self.zero()
-        cdef Py_ssize_t l
+        cdef Py_ssize_t l = 0
         for e in D:
             l = len(e)
             break

src/sage/calculus/transforms/dwt.pyx

@@ -142,6 +142,8 @@ cdef class DiscreteWaveletTransform(GSLDoubleArray):
         from sage.plot.point import point
 
         cdef int i
+        cdef int x_min = 0
+        cdef int x_max = 0
         cdef double x
         v = []
         if xmin is None:

src/sage/combinat/crystals/pbw_datum.pyx

@@ -452,8 +452,8 @@ cpdef list enhance_braid_move_chain(braid_move_chain, cartan_type):
         sage: enhanced_chain[7]
         ((3, 6), (-1, -1))
     """
-    cdef int i, j
-    cdef int k, pos, first, last
+    cdef int i = 0, j = 0
+    cdef int k = 0, pos, first = 0, last = 0
     cdef tuple cartan_sub_matrix
     cdef list output_list = []
     output_list.append( (None, None) )

src/sage/combinat/enumeration_mod_permgroup.pyx

@@ -72,7 +72,7 @@ cpdef int lex_cmp_partial(ClonableIntArray v1, ClonableIntArray v2, int step) no
         sage: lex_cmp_partial(IA([0,1,2,3]),IA([0,1,2,4]),4)
         -1
     """
-    cdef int i
+    cdef int i = 0
     if step < 0 or step > v1._len or step > v2._len:
         raise IndexError("list index out of range")
 
@@ -271,7 +271,7 @@ cpdef set orbit(list sgs, ClonableIntArray v):
         sage: sorted(orbit(sgs, IA([1,2,3,4])))
         [[1, 2, 3, 4], [2, 3, 4, 1], [3, 4, 1, 2], [4, 1, 2, 3]]
     """
-    cdef i,l
+    cdef i = 0, l = 0
     cdef set to_analyse, new_to_analyse
     cdef ClonableIntArray list_test, child
     cdef PermutationGroupElement x

src/sage/combinat/matrices/dancing_links_c.h

@@ -253,6 +253,8 @@ class dancing_links {
         current_node = NULL;
         best_col = NULL;
         search_started = false;
+        root = NULL;
+        mode = SEARCH_FORWARD;
     }
 
     ~dancing_links()

src/sage/dynamics/arithmetic_dynamics/projective_ds_helper.pyx

@@ -256,7 +256,7 @@ cpdef _normalize_coordinates(list point, int prime, int len_points):
         sage: L
         [1, 2, 1]
     """
-    cdef int last_coefficient, coefficient, mod_inverse, val
+    cdef int last_coefficient = 0, coefficient, mod_inverse, val
 
     for coefficient in range(len_points):
         val = ((<int> point[coefficient]) + prime) % prime

src/sage/dynamics/complex_dynamics/mandel_julia_helper.pyx

@@ -115,7 +115,7 @@ cpdef fast_mandelbrot_plot(double x_center, double y_center,
 
     cdef:
         M, pixel, color_list
-        long i, j, col, row, level, iteration
+        long i, j, col, row, level, iteration = 0
         double x_corner, y_corner, step_size, x_coor, y_coor, new_x, new_y
 
     # Make sure image_width is positive

src/sage/geometry/triangulation/data.cc

@@ -107,9 +107,9 @@ vertices vertices_lookup::manual_vertices_to_simplex(const simplex & S) const
   vertices result;
   simplex s=S;
   simplex b;
-  vertex i,j,l=0,k;
+  vertex j,l=0,k;
   for (k=1; k<d; k++) {
-    l++;  i=l;   j=1;
+    l++;  j=1;
     b=binomial(n-l,d-k);
     while (s>b && b>0) {
       j++;  l++;

src/sage/geometry/triangulation/data.h

@@ -39,7 +39,7 @@ class vertices: public std::set<vertex,std::less<vertex> >
   void set_dimensions(int N, int D);
   friend std::ostream & operator << (std::ostream &, const vertices &);
   friend bool operator==(const vertices &, const vertices &);
-  bool full_set() const { return this->size() == n; }
+  bool full_set() const { return this->size() == static_cast<size_t>(n); }
 };
 
 // tables used by vertices to make computation faster

src/sage/geometry/triangulation/triangulations.cc

@@ -80,7 +80,7 @@ void triangulations::add_neighbours(const simplices & s)
 
 bool triangulations::have_more_triangulations()
 {
-  while (position != this->size()) {
+  while (position != static_cast<int>(this->size())) {
      // eat all non-star triangulations
     simplices triangulation((*this)[position]);
 

src/sage/graphs/base/boost_interface.cpp

@@ -247,7 +247,7 @@ class BoostGraph
 
          to_return.distances = distances;
 
-         for (int i = 0; i < N; i++) {
+         for (v_index i = 0; i < N; i++) {
              to_return.predecessors.push_back(index[predecessors[i]]);
          }
 
@@ -274,7 +274,7 @@ class BoostGraph
          }
 
          to_return.distances = distance;
-         for (int i = 0; i < N; i++) {
+         for (v_index i = 0; i < N; i++) {
              to_return.predecessors.push_back(index[predecessors[i]]);
          }
          return to_return;

src/sage/graphs/base/c_graph.pyx

@@ -3156,7 +3156,7 @@ cdef class CGraphBackend(GenericGraphBackend):
         cdef FrozenBitset b_vertices
         cdef int n_vertices = len(vertices)
         cdef bint loops = other.loops()
-        cdef bint multiple_edges
+        cdef bint multiple_edges = False
         if modus == 0:
             multiple_edges = self.multiple_edges(None) and other.multiple_edges(None)
         elif 1 <= modus <= 2:
@@ -3893,7 +3893,7 @@ cdef class CGraphBackend(GenericGraphBackend):
         # which defines the shortest path found
         # (of length shortest_path_length).
         cdef int meeting_vertex = -1
-        cdef double shortest_path_length
+        cdef double shortest_path_length = 0
         cdef double f_tmp
 
         if reduced_weight is not None:
@@ -4107,7 +4107,7 @@ cdef class CGraphBackend(GenericGraphBackend):
         # which defines the shortest path found
         # (of length shortest_path_length).
         cdef int meeting_vertex = -1
-        cdef double shortest_path_length
+        cdef double shortest_path_length = 0
         cdef double f_tmp
 
         if weight_function is None:

src/sage/graphs/comparability.pyx

@@ -818,7 +818,7 @@ def is_transitive(g, certificate=False):
     cdef bitset_t seen
     bitset_init(seen, n)
 
-    cdef uint32_t u, v
+    cdef uint32_t u, v = 0
     cdef int i
 
     for u in range(n):

src/sage/graphs/distances_all_pairs.pyx

@@ -865,7 +865,7 @@ cdef uint32_t * c_eccentricity_DHV(short_digraph sd) except NULL:
     cdef uint32_t u, ecc_u
     cdef uint32_t antipode, ecc_antipode
     cdef uint32_t v, tmp
-    cdef size_t i, idx
+    cdef size_t i, idx = 0
     cdef bitset_t seen
     bitset_init(seen, n)
 
@@ -1592,7 +1592,7 @@ cdef uint32_t diameter_DHV(short_digraph g) noexcept:
     cdef uint32_t LB = 0
     cdef uint32_t UB = UINT32_MAX
     cdef uint32_t v, tmp
-    cdef size_t i, idx
+    cdef size_t i, idx = 0
     cdef bitset_t seen
     bitset_init(seen, n)
 

src/sage/graphs/graph_decompositions/bandwidth.pyx

@@ -252,7 +252,7 @@ def bandwidth(G, k=None):
     cdef range_t ** ith_range_array = <range_t **> mem.allocarray(n, sizeof(range_t *))
     cdef range_t * range_array_tmp = <range_t *> mem.allocarray(n, sizeof(range_t))
 
-    cdef int i, kk
+    cdef int i, kk = 0
     # compute the distance matrix
     all_pairs_shortest_path_BFS(G, NULL, distances, NULL, vertex_list=int_to_vertex)
 

src/sage/groups/perm_gps/partn_ref/automorphism_group_canonical_label.pyx

@@ -450,15 +450,15 @@ cdef aut_gp_and_can_lab *get_aut_gp_and_can_lab(void *S,
     """
     cdef PartitionStack *current_ps
     cdef PartitionStack *first_ps
-    cdef PartitionStack *label_ps
+    cdef PartitionStack *label_ps = NULL
     cdef int first_meets_current = -1
-    cdef int label_meets_current
+    cdef int label_meets_current = 0
     cdef int current_kids_are_same = 1
     cdef int first_kids_are_same
 
     cdef int *current_indicators
     cdef int *first_indicators
-    cdef int *label_indicators
+    cdef int *label_indicators = NULL
     cdef int first_and_current_indicator_same
     cdef int label_and_current_indicator_same = -1
     cdef int compared_current_and_label_indicators
@@ -467,7 +467,7 @@ cdef aut_gp_and_can_lab *get_aut_gp_and_can_lab(void *S,
     cdef OrbitPartition *orbits_of_permutation
     cdef OrbitPartition *orbits_of_supergroup
     cdef int subgroup_primary_orbit_size = 0
-    cdef int minimal_in_primary_orbit
+    cdef int minimal_in_primary_orbit = 0
 
     cdef bitset_t *fixed_points_of_generators # i.e. fp
     cdef bitset_t *minimal_cell_reps_of_generators # i.e. mcr
@@ -482,7 +482,7 @@ cdef aut_gp_and_can_lab *get_aut_gp_and_can_lab(void *S,
     cdef int *vertices_determining_current_stack
     cdef int *perm_stack
     cdef StabilizerChain *group = NULL
-    cdef StabilizerChain *old_group
+    cdef StabilizerChain *old_group = NULL
     cdef StabilizerChain *tmp_gp
 
     cdef int i, j, k, ell, b

src/sage/groups/perm_gps/partn_ref/data_structures.pyx

@@ -1769,7 +1769,7 @@ cdef int compute_relabeling(StabilizerChain *group, StabilizerChain *scratch_gro
     """
     Technically, compute the INVERSE of the relabeling
     """
-    cdef int i, j, x, y, m, n = group.degree, orbit_element
+    cdef int i, j, x, y = 0, m, n = group.degree, orbit_element
     cdef int *scratch = group.perm_scratch
     if SC_new_base_nomalloc(scratch_group, group, permutation, n):
         return 1

src/sage/groups/perm_gps/partn_ref/double_coset.pyx

@@ -333,7 +333,7 @@ cdef int double_coset(void *S1, void *S2, PartitionStack *partition1, int *order
     cdef OrbitPartition *orbits_of_subgroup
     cdef OrbitPartition *orbits_of_supergroup
     cdef int subgroup_primary_orbit_size = 0
-    cdef int minimal_in_primary_orbit
+    cdef int minimal_in_primary_orbit = 0
 
     cdef bitset_t *fixed_points_of_generators # i.e. fp
     cdef bitset_t *minimal_cell_reps_of_generators # i.e. mcr
@@ -347,8 +347,8 @@ cdef int double_coset(void *S1, void *S2, PartitionStack *partition1, int *order
     cdef int *cells_to_refine_by
     cdef int *vertices_determining_current_stack
     cdef int *perm_stack
-    cdef StabilizerChain *group
-    cdef StabilizerChain *old_group
+    cdef StabilizerChain *group = NULL
+    cdef StabilizerChain *old_group = NULL
     cdef StabilizerChain *tmp_gp
 
     cdef int i, j, k, ell, b

src/sage/groups/perm_gps/partn_ref2/refinement_generic.pyx

@@ -721,7 +721,7 @@ cdef class PartitionRefinement_generic:
         `I`) and compute the `(I+J)`-semicanonical representative.
         """
         cdef bint loc_inner_group_changed, reset_allowance_best = False
-        cdef int i, j, best_end, best_ind
+        cdef int i, j, best_end = 0, best_ind = 0
 
         if self._is_candidate_initialized:
             allowance_best = self._allowance_best[self._nr_of_inner_min_unmin_calls]

src/sage/groups/perm_gps/permgroup_element.pyx

@@ -762,7 +762,7 @@ cdef class PermutationGroupElement(MultiplicativeGroupElement):
             ValueError: invalid string to initialize a permutation
         """
         cdef Py_ssize_t i=0, j
-        cdef int k, m
+        cdef int k = 0, m = 0
         cdef str c
         cdef list cycle
         cdef dict convert_dict = self._parent._domain_to_gap

src/sage/lfunctions/zero_sums.pyx

@@ -1154,9 +1154,9 @@ cdef class LFunctionZeroSum_EllipticCurve(LFunctionZeroSum_abstract):
         cdef double twopi = npi * 2
         cdef double eg = self._euler_gamma
 
-        cdef double t, u, w, y, z, expt, bound1, logp, logq
-        cdef double thetap, thetaq, sqrtp, sqrtq, p, q
-        cdef int ap, aq
+        cdef double t, u, w, y, z = 0, expt, bound1, logp = 0, logq = 0
+        cdef double thetap = 0, thetaq = 0, sqrtp = 0, sqrtq = 0, p = 0, q
+        cdef int ap = 0, aq
 
         cdef unsigned long n
         cdef double N_double = self._level
@@ -1439,9 +1439,9 @@ cdef class LFunctionZeroSum_EllipticCurve(LFunctionZeroSum_abstract):
         cdef double eg = self._euler_gamma
         cdef double N_double = self._level
 
-        cdef double t, u, w, y, z, expt, bound1, logp, logq
-        cdef double thetap, thetaq, sqrtp, sqrtq, p, q
-        cdef int ap, aq
+        cdef double t, u, w, y, z = 0, expt, bound1, logp = 0, logq = 0
+        cdef double thetap = 0, thetaq = 0, sqrtp = 0, sqrtq = 0, p = 0, q
+        cdef int ap = 0, aq
         cdef unsigned long n
 
         # Compute bounds and smooth part of sum

src/sage/libs/ntl/ntlwrap_impl.h

@@ -4,6 +4,12 @@
 
 #ifdef __cplusplus
 
+/* Suppress unused-function warnings since this header contains optional utility functions */
+#if defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
+#endif
+
 #include <iostream>
 #include <sstream>
 #include <gmp.h>
@@ -737,5 +743,9 @@ static void ZZ_pX_InvMod_newton_ram(struct ZZ_pX &x, const struct ZZ_pX &a, cons
     delete xn;
 }
 
+#if defined(__GNUC__)
+#pragma GCC diagnostic pop
+#endif
+
 #endif  /* #ifdef __cplusplus */
 #endif  /* #ifndef  _SAGE_NTLWRAP_CPP */

src/sage/matrix/matrix0.pyx

@@ -966,7 +966,7 @@ cdef class Matrix(sage.structure.element.Matrix):
         cdef list row_list
         cdef list col_list
         cdef Py_ssize_t i
-        cdef int row, col
+        cdef int row = 0, col = 0
         cdef int nrows = self._nrows
         cdef int ncols = self._ncols
         cdef tuple key_tuple
@@ -1443,7 +1443,7 @@ cdef class Matrix(sage.structure.element.Matrix):
         cdef list value_list
         cdef bint value_list_one_dimensional = 0
         cdef Py_ssize_t i
-        cdef Py_ssize_t row, col
+        cdef Py_ssize_t row = 0, col = 0
         cdef Py_ssize_t nrows = self._nrows
         cdef Py_ssize_t ncols = self._ncols
         cdef tuple key_tuple

src/sage/matrix/matrix_gf2e_dense.pyx

@@ -1468,7 +1468,7 @@ cdef class Matrix_gf2e_dense(matrix_dense.Matrix_dense):
         from sage.matrix.matrix_space import MatrixSpace
 
         cdef Matrix_mod2_dense A
-        cdef int r,c
+        cdef int r = 0, c = 0
 
         r, c = self.nrows(), self.ncols()
         if r == 0 or c == 0: