diff --git a/stdlib/SparseArrays/src/higherorderfns.jl b/stdlib/SparseArrays/src/higherorderfns.jl
index 66ab8b3f60e52..1672880b35c71 100644
--- a/stdlib/SparseArrays/src/higherorderfns.jl
+++ b/stdlib/SparseArrays/src/higherorderfns.jl
@@ -9,7 +9,8 @@ import Base: map, map!, broadcast, copy, copyto!
 using Base: front, tail, to_shape
 using ..SparseArrays: SparseVector, SparseMatrixCSC, AbstractSparseVector,
                       AbstractSparseMatrix, AbstractSparseArray, indtype, nnz, nzrange,
-                      SparseVectorUnion, AdjOrTransSparseVectorUnion, nonzeroinds, nonzeros
+                      SparseVectorUnion, AdjOrTransSparseVectorUnion, nonzeroinds, nonzeros,
+                      spzeros
 using Base.Broadcast: BroadcastStyle, Broadcasted, flatten
 using LinearAlgebra
 
@@ -126,17 +127,30 @@ const SpBroadcasted2{Style<:SPVM,Axes,F,Args<:Tuple{SparseVecOrMat,SparseVecOrMa
 @inline storedvals(A::SparseVecOrMat) = A.nzval
 @inline setcolptr!(A::SparseVector, j, val) = val
 @inline setcolptr!(A::SparseMatrixCSC, j, val) = A.colptr[j] = val
-function trimstorage!(A::SparseVecOrMat, maxstored)
-    resize!(storedinds(A), maxstored)
-    resize!(storedvals(A), maxstored)
-    return maxstored
-end
+
 function expandstorage!(A::SparseVecOrMat, maxstored)
-    length(storedinds(A)) < maxstored && resize!(storedinds(A), maxstored)
-    length(storedvals(A)) < maxstored && resize!(storedvals(A), maxstored)
+    if _capacity(A) < maxstored
+        sizehint!(storedinds(A), maxstored)
+        sizehint!(storedvals(A), maxstored)
+    end
     return maxstored
 end
 
+function _reset!(C::SparseVector)
+    empty!(C.nzind)
+    empty!(C.nzval)
+end
+
+function _reset!(C::SparseMatrixCSC)
+    fill!(C.colptr, 1)
+    empty!(C.rowval)
+    empty!(C.nzval)
+end
+
+_checkbuffers(S::SparseMatrixCSC) = (@assert length(S.colptr) == S.n + 1 && S.colptr[end] - 1 == length(S.rowval) == length(S.nzval); S)
+_checkbuffers(S::SparseVector) = (@assert length(S.nzval) == length(S.nzind); S)
+
+_capacity(A::SparseVecOrMat) = capacity(storedinds(A))
 
 # (2) map[!] entry points
 map(f::Tf, A::SparseVector) where {Tf} = _noshapecheck_map(f, A)
@@ -169,18 +183,17 @@ end
 copy(bc::SpBroadcasted1) = _noshapecheck_map(bc.f, bc.args[1])
 
 @inline function copyto!(C::SparseVecOrMat, bc::Broadcasted0{Nothing})
-    isempty(C) && return _finishempty!(C)
+    isempty(C) && return _checkbuffers(C)
     f = bc.f
     fofnoargs = f()
     if _iszero(fofnoargs) # f() is zero, so empty C
-        trimstorage!(C, 0)
-        _finishempty!(C)
+        _reset!(C)
     else # f() is nonzero, so densify C and fill with independent calls to f()
         _densestructure!(C)
         storedvals(C)[1] = fofnoargs
         broadcast!(f, view(storedvals(C), 2:length(storedvals(C))))
     end
-    return C
+    return _checkbuffers(C)
 end
 
 function _diffshape_broadcast(f::Tf, A::SparseVecOrMat, Bs::Vararg{SparseVecOrMat,N}) where {Tf,N}
@@ -223,22 +236,13 @@ _maxnnzfrom(shape::NTuple{2}, A::SparseMatrixCSC) = nnz(A) * div(shape[1], A.m)
 @inline _unchecked_maxnnzbcres(shape, As...) = _unchecked_maxnnzbcres(shape, As)
 @inline _checked_maxnnzbcres(shape::NTuple{1}, As...) = shape[1] != 0 ? _unchecked_maxnnzbcres(shape, As) : 0
 @inline _checked_maxnnzbcres(shape::NTuple{2}, As...) = shape[1] != 0 && shape[2] != 0 ? _unchecked_maxnnzbcres(shape, As) : 0
-@inline function _allocres(shape::NTuple{1}, indextype, entrytype, maxnnz)
-    storedinds = Vector{indextype}(undef, maxnnz)
-    storedvals = Vector{entrytype}(undef, maxnnz)
-    return SparseVector(shape..., storedinds, storedvals)
-end
-@inline function _allocres(shape::NTuple{2}, indextype, entrytype, maxnnz)
-    pointers = Vector{indextype}(undef, shape[2] + 1)
-    storedinds = Vector{indextype}(undef, maxnnz)
-    storedvals = Vector{entrytype}(undef, maxnnz)
-    return SparseMatrixCSC(shape..., pointers, storedinds, storedvals)
-end
+@inline _allocres(shape::NTuple, indextype, entrytype, maxnnz) = sizehint!(spzeros(entrytype, indextype, shape...), maxnnz)
 
 # (4) _map_zeropres!/_map_notzeropres! specialized for a single sparse vector/matrix
 "Stores only the nonzero entries of `map(f, Array(A))` in `C`."
 function _map_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat) where Tf
-    spaceC::Int = min(length(storedinds(C)), length(storedvals(C)))
+    _reset!(C)
+    spaceC::Int = _capacity(C)
     Ck = 1
     @inbounds for j in columns(C)
         setcolptr!(C, j, Ck)
@@ -246,15 +250,14 @@ function _map_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat) where Tf
             Cx = f(storedvals(A)[Ak])
             if !_iszero(Cx)
                 Ck > spaceC && (spaceC = expandstorage!(C, Ck + nnz(A) - (Ak - 1)))
-                storedinds(C)[Ck] = storedinds(A)[Ak]
-                storedvals(C)[Ck] = Cx
+                push!(storedinds(C), storedinds(A)[Ak])
+                push!(storedvals(C), Cx)
                 Ck += 1
             end
         end
     end
     @inbounds setcolptr!(C, numcols(C) + 1, Ck)
-    trimstorage!(C, Ck - 1)
-    return C
+    return _checkbuffers(C)
 end
 """
 Densifies `C`, storing `fillvalue` in place of each unstored entry in `A` and
@@ -273,19 +276,21 @@ function _map_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseVecOrMa
     end
     # NOTE: Combining the fill! above into the loop above to avoid multiple sweeps over /
     # nonsequential access of storedvals(C) does not appear to improve performance.
-    return C
+    return _checkbuffers(C)
 end
 # helper functions for these methods and some of those below
 @inline _densecoloffsets(A::SparseVector) = 0
 @inline _densecoloffsets(A::SparseMatrixCSC) = 0:A.m:(A.m*(A.n - 1))
 function _densestructure!(A::SparseVector)
-    expandstorage!(A, A.n)
+    resize!(A.nzval, A.n)
+    resize!(A.nzind, A.n)
     copyto!(A.nzind, 1:A.n)
     return A
 end
 function _densestructure!(A::SparseMatrixCSC)
     nnzA = A.m * A.n
-    expandstorage!(A, nnzA)
+    resize!(A.rowval, nnzA)
+    resize!(A.nzval, nnzA)
     copyto!(A.colptr, 1:A.m:(nnzA + 1))
     for k in _densecoloffsets(A)
         copyto!(A.rowval, k + 1, 1:A.m)
@@ -296,7 +301,8 @@ end
 
 # (5) _map_zeropres!/_map_notzeropres! specialized for a pair of sparse vectors/matrices
 function _map_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::SparseVecOrMat) where Tf
-    spaceC::Int = min(length(storedinds(C)), length(storedvals(C)))
+    _reset!(C)
+    spaceC::Int = _capacity(C)
     rowsentinelA = convert(indtype(A), numrows(C) + 1)
     rowsentinelB = convert(indtype(B), numrows(C) + 1)
     Ck = 1
@@ -327,15 +333,14 @@ function _map_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::SparseVe
             # corresponding broadcast code (below).
             if !_iszero(Cx)
                 Ck > spaceC && (spaceC = expandstorage!(C, Ck + (nnz(A) - (Ak - 1)) + (nnz(B) - (Bk - 1))))
-                storedinds(C)[Ck] = Ci
-                storedvals(C)[Ck] = Cx
+                push!(storedinds(C), Ci)
+                push!(storedvals(C), Cx)
                 Ck += 1
             end
         end
     end
     @inbounds setcolptr!(C, numcols(C) + 1, Ck)
-    trimstorage!(C, Ck - 1)
-    return C
+    return _checkbuffers(C)
 end
 function _map_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseVecOrMat, B::SparseVecOrMat) where Tf
     # Build dense matrix structure in C, expanding storage if necessary
@@ -367,13 +372,14 @@ function _map_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseVecOrMa
             Cx != fillvalue && (storedvals(C)[jo + Ci] = Cx)
         end
     end
-    return C
+    return _checkbuffers(C)
 end
 
 
 # (6) _map_zeropres!/_map_notzeropres! for more than two sparse matrices / vectors
 function _map_zeropres!(f::Tf, C::SparseVecOrMat, As::Vararg{SparseVecOrMat,N}) where {Tf,N}
-    spaceC::Int = min(length(storedinds(C)), length(storedvals(C)))
+    _reset!(C)
+    spaceC::Int = _capacity(C)
     rowsentinel = numrows(C) + 1
     Ck = 1
     stopks = _colstartind_all(1, As)
@@ -388,16 +394,15 @@ function _map_zeropres!(f::Tf, C::SparseVecOrMat, As::Vararg{SparseVecOrMat,N})
             Cx = f(vals...)
             if !_iszero(Cx)
                 Ck > spaceC && (spaceC = expandstorage!(C, Ck + min(length(C), _sumnnzs(As...)) - (sum(ks) - N)))
-                storedinds(C)[Ck] = activerow
-                storedvals(C)[Ck] = Cx
+                push!(storedinds(C), activerow)
+                push!(storedvals(C), Cx)
                 Ck += 1
             end
             activerow = min(rows...)
         end
     end
     @inbounds setcolptr!(C, numcols(C) + 1, Ck)
-    trimstorage!(C, Ck - 1)
-    return C
+    return _checkbuffers(C)
 end
 function _map_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, As::Vararg{SparseVecOrMat,N}) where {Tf,N}
     # Build dense matrix structure in C, expanding storage if necessary
@@ -420,7 +425,7 @@ function _map_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, As::Vararg{Spars
             activerow = min(rows...)
         end
     end
-    return C
+    return _checkbuffers(C)
 end
 
 # helper methods for map/map! methods just above
@@ -460,8 +465,9 @@ end
 
 # (7) _broadcast_zeropres!/_broadcast_notzeropres! specialized for a single (input) sparse vector/matrix
 function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat) where Tf
-    isempty(C) && return _finishempty!(C)
-    spaceC::Int = min(length(storedinds(C)), length(storedvals(C)))
+    isempty(C) && return _checkbuffers(C)
+    _reset!(C)
+    spaceC::Int = _capacity(C)
     # C and A cannot have the same shape, as we directed that case to map in broadcast's
     # entry point; here we need efficiently handle only heterogeneous C-A combinations where
     # one or both of C and A has at least one singleton dimension.
@@ -479,8 +485,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat) where
                 Cx = f(storedvals(A)[Ak])
                 if !_iszero(Cx)
                     Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A)))
-                    storedinds(C)[Ck] = storedinds(A)[Ak]
-                    storedvals(C)[Ck] = Cx
+                    push!(storedinds(C), storedinds(A)[Ak])
+                    push!(storedvals(C), Cx)
                     Ck += 1
                 end
             end
@@ -499,16 +505,15 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat) where
             if !_iszero(fofAx)
                 for Ci::indtype(C) in 1:numrows(C)
                     Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A)))
-                    storedinds(C)[Ck] = Ci
-                    storedvals(C)[Ck] = fofAx
+                    push!(storedinds(C), Ci)
+                    push!(storedvals(C), fofAx)
                     Ck += 1
                 end
             end
         end
     end
     @inbounds setcolptr!(C, numcols(C) + 1, Ck)
-    trimstorage!(C, Ck - 1)
-    return C
+    return _checkbuffers(C)
 end
 function _broadcast_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseVecOrMat) where Tf
     # For information on this code, see comments in similar code in _broadcast_zeropres! above
@@ -539,14 +544,15 @@ function _broadcast_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseV
             end
         end
     end
-    return C
+    return _checkbuffers(C)
 end
 
 
 # (8) _broadcast_zeropres!/_broadcast_notzeropres! specialized for a pair of (input) sparse vectors/matrices
 function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::SparseVecOrMat) where Tf
-    isempty(C) && return _finishempty!(C)
-    spaceC::Int = min(length(storedinds(C)), length(storedvals(C)))
+    isempty(C) && return _checkbuffers(C)
+    _reset!(C)
+    spaceC::Int = _capacity(C)
     rowsentinelA = convert(indtype(A), numrows(C) + 1)
     rowsentinelB = convert(indtype(B), numrows(C) + 1)
     # C, A, and B cannot all have the same shape, as we directed that case to map in broadcast's
@@ -601,8 +607,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
                 # chain above differs from that in the corresponding map code.
                 if !_iszero(Cx)
                     Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A, B)))
-                    storedinds(C)[Ck] = Ci
-                    storedvals(C)[Ck] = Cx
+                    push!(storedinds(C), Ci)
+                    push!(storedvals(C), Cx)
                     Ck += 1
                 end
             end
@@ -619,8 +625,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
             if !_iszero(Cx)
                 for Ci::indtype(C) in 1:numrows(C)
                     Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A, B)))
-                    storedinds(C)[Ck] = Ci
-                    storedvals(C)[Ck] = Cx
+                    push!(storedinds(C), Ci)
+                    push!(storedvals(C), Cx)
                     Ck += 1
                 end
             end
@@ -640,8 +646,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
                     Cx = f(Ax, storedvals(B)[Bk])
                     if !_iszero(Cx)
                         Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A, B)))
-                        storedinds(C)[Ck] = storedinds(B)[Bk]
-                        storedvals(C)[Ck] = Cx
+                        push!(storedinds(C), storedinds(B)[Bk])
+                        push!(storedvals(C), Cx)
                         Ck += 1
                     end
                     Bk += oneunit(Bk)
@@ -659,8 +665,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
                     end
                     if !_iszero(Cx)
                         Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A, B)))
-                        storedinds(C)[Ck] = Ci
-                        storedvals(C)[Ck] = Cx
+                        push!(storedinds(C), Ci)
+                        push!(storedvals(C), Cx)
                         Ck += 1
                     end
                 end
@@ -681,8 +687,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
                     Cx = f(storedvals(A)[Ak], Bx)
                     if !_iszero(Cx)
                         Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A, B)))
-                        storedinds(C)[Ck] = storedinds(A)[Ak]
-                        storedvals(C)[Ck] = Cx
+                        push!(storedinds(C), storedinds(A)[Ak])
+                        push!(storedvals(C), Cx)
                         Ck += 1
                     end
                     Ak += oneunit(Ak)
@@ -700,8 +706,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
                     end
                     if !_iszero(Cx)
                         Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), A, B)))
-                        storedinds(C)[Ck] = Ci
-                        storedvals(C)[Ck] = Cx
+                        push!(storedinds(C), Ci)
+                        push!(storedvals(C), Cx)
                         Ck += 1
                     end
                 end
@@ -709,8 +715,7 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, A::SparseVecOrMat, B::Sp
         end
     end
     @inbounds setcolptr!(C, numcols(C) + 1, Ck)
-    trimstorage!(C, Ck - 1)
-    return C
+    return _checkbuffers(C)
 end
 function _broadcast_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseVecOrMat, B::SparseVecOrMat) where Tf
     # For information on this code, see comments in similar code in _broadcast_zeropres! above
@@ -809,10 +814,8 @@ function _broadcast_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, A::SparseV
             end
         end
     end
-    return C
+    return _checkbuffers(C)
 end
-_finishempty!(C::SparseVector) = C
-_finishempty!(C::SparseMatrixCSC) = (fill!(C.colptr, 1); C)
 
 # special case - vector outer product
 _copy(f::typeof(*), x::SparseVectorUnion, y::AdjOrTransSparseVectorUnion) = _outer(x, y)
@@ -853,14 +856,16 @@ function _outer(trans::Tf, x, y) where Tf
         end
     end
     cumsum!(colptrC, colptrC)
-
+    resize!(rowvalC, idx)
+    resize!(nzvalsC, idx)
     return SparseMatrixCSC(nx, ny, colptrC, rowvalC, nzvalsC)
 end
 
 # (9) _broadcast_zeropres!/_broadcast_notzeropres! for more than two (input) sparse vectors/matrices
 function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, As::Vararg{SparseVecOrMat,N}) where {Tf,N}
-    isempty(C) && return _finishempty!(C)
-    spaceC::Int = min(length(storedinds(C)), length(storedvals(C)))
+    isempty(C) && return _checkbuffers(C)
+    _reset!(C)
+    spaceC::Int = _capacity(C)
     expandsverts = _expandsvert_all(C, As)
     expandshorzs = _expandshorz_all(C, As)
     rowsentinel = numrows(C) + 1
@@ -882,8 +887,8 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, As::Vararg{SparseVecOrMa
                 Cx = f(args...)
                 if !_iszero(Cx)
                     Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), As)))
-                    storedinds(C)[Ck] = activerow
-                    storedvals(C)[Ck] = Cx
+                    push!(storedinds(C), activerow)
+                    push!(storedvals(C), Cx)
                     Ck += 1
                 end
                 activerow = min(rows...)
@@ -899,19 +904,18 @@ function _broadcast_zeropres!(f::Tf, C::SparseVecOrMat, As::Vararg{SparseVecOrMa
                 end
                 if !_iszero(Cx)
                     Ck > spaceC && (spaceC = expandstorage!(C, _unchecked_maxnnzbcres(size(C), As)))
-                    storedinds(C)[Ck] = Ci
-                    storedvals(C)[Ck] = Cx
+                    push!(storedinds(C), Ci)
+                    push!(storedvals(C), Cx)
                     Ck += 1
                 end
             end
         end
     end
     @inbounds setcolptr!(C, numcols(C) + 1, Ck)
-    trimstorage!(C, Ck - 1)
-    return C
+    return _checkbuffers(C)
 end
 function _broadcast_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, As::Vararg{SparseVecOrMat,N}) where {Tf,N}
-    isempty(C) && return _finishempty!(C)
+    isempty(C) && return _checkbuffers(C)
     # Build dense matrix structure in C, expanding storage if necessary
     _densestructure!(C)
     # Populate values
@@ -949,7 +953,7 @@ function _broadcast_notzeropres!(f::Tf, fillvalue, C::SparseVecOrMat, As::Vararg
             end
         end
     end
-    return C
+    return _checkbuffers(C)
 end
 
 # helper method for broadcast/broadcast! methods just above
diff --git a/stdlib/SparseArrays/src/sparsematrix.jl b/stdlib/SparseArrays/src/sparsematrix.jl
index 6c8037bd6bfe2..9e6f816c79333 100644
--- a/stdlib/SparseArrays/src/sparsematrix.jl
+++ b/stdlib/SparseArrays/src/sparsematrix.jl
@@ -26,6 +26,7 @@ struct SparseMatrixCSC{Tv,Ti<:Integer} <: AbstractSparseMatrix{Tv,Ti}
             throw(ArgumentError("number of $str ($lbl) must be ≥ 0, got $k"))
         m < 0 && throwsz("rows", 'm', m)
         n < 0 && throwsz("columns", 'n', n)
+        _goodbuffers(Int(n), colptr, rowval, nzval) || throw(ArgumentError("Illegal buffers for SparseMatrixCSC construction $n $colptr $rowval $nzval"))
         new(Int(m), Int(n), colptr, rowval, nzval)
     end
 end
@@ -35,6 +36,13 @@ function SparseMatrixCSC(m::Integer, n::Integer, colptr::Vector, rowval::Vector,
     SparseMatrixCSC{Tv,Ti}(m, n, colptr, rowval, nzval)
 end
 
+
+
+_goodbuffers(n, colptr, rowval, nzval) = length(colptr) == n + 1 && colptr[end] - 1 == length(rowval) == length(nzval)
+_goodbuffers(S::SparseMatrixCSC) = _goodbuffers(S.n, S.colptr, S.rowval, S.nzval)
+_checkbuffers(S::SparseMatrixCSC) = (@assert _goodbuffers(S); S)
+
+
 size(S::SparseMatrixCSC) = (S.m, S.n)
 
 # Define an alias for views of a SparseMatrixCSC which include all rows and a unit range of the columns.
@@ -152,6 +160,7 @@ nzrange(S::SparseMatrixCSC, col::Integer) = S.colptr[col]:(S.colptr[col+1]-1)
 nzrange(S::SparseMatrixCSCView, col::Integer) = nzrange(S.parent, S.indices[2][col])
 
 function Base.show(io::IO, ::MIME"text/plain", S::SparseMatrixCSC)
+    _checkbuffers(S)
     xnnz = nnz(S)
     print(io, S.m, "×", S.n, " ", typeof(S), " with ", xnnz, " stored ",
               xnnz == 1 ? "entry" : "entries")
@@ -163,6 +172,7 @@ end
 
 Base.show(io::IO, S::SparseMatrixCSC) = Base.show(convert(IOContext, io), S::SparseMatrixCSC)
 function Base.show(io::IOContext, S::SparseMatrixCSC)
+    _checkbuffers(S)
     if nnz(S) == 0
         return show(io, MIME("text/plain"), S)
     end
@@ -216,7 +226,7 @@ end
 
 ## Reshape
 
-function sparse_compute_reshaped_colptr_and_rowval(colptrS::Vector{Ti}, rowvalS::Vector{Ti},
+function sparse_compute_reshaped_colptr_and_rowval!(colptrS::Vector{Ti}, rowvalS::Vector{Ti},
                                                    mS::Int, nS::Int, colptrA::Vector{Ti},
                                                    rowvalA::Vector{Ti}, mA::Int, nA::Int) where Ti
     lrowvalA = length(rowvalA)
@@ -259,7 +269,7 @@ function copy(ra::ReshapedArray{<:Any,2,<:SparseMatrixCSC})
     rowval = similar(a.rowval)
     nzval = copy(a.nzval)
 
-    sparse_compute_reshaped_colptr_and_rowval(colptr, rowval, mS, nS, a.colptr, a.rowval, mA, nA)
+    sparse_compute_reshaped_colptr_and_rowval!(colptr, rowval, mS, nS, a.colptr, a.rowval, mA, nA)
 
     return SparseMatrixCSC(mS, nS, colptr, rowval, nzval)
 end
@@ -286,7 +296,7 @@ function copyto!(A::SparseMatrixCSC, B::SparseMatrixCSC)
             copyto!(A.rowval, B.rowval)
         else
             # This is like a "reshape B into A".
-            sparse_compute_reshaped_colptr_and_rowval(A.colptr, A.rowval, A.m, A.n, B.colptr, B.rowval, B.m, B.n)
+            sparse_compute_reshaped_colptr_and_rowval!(A.colptr, A.rowval, A.m, A.n, B.colptr, B.rowval, B.m, B.n)
         end
     else
         length(A) >= length(B) || throw(BoundsError())
@@ -316,10 +326,10 @@ function copyto!(A::SparseMatrixCSC, B::SparseMatrixCSC)
         @inbounds for i in 2:length(A.colptr)
             A.colptr[i] += nnzB - lastmodptrA
         end
-        sparse_compute_reshaped_colptr_and_rowval(A.colptr, A.rowval, A.m, lastmodcolA-1, B.colptr, B.rowval, B.m, B.n)
+        sparse_compute_reshaped_colptr_and_rowval!(A.colptr, A.rowval, A.m, lastmodcolA-1, B.colptr, B.rowval, B.m, B.n)
     end
     copyto!(A.nzval, B.nzval)
-    return A
+    return _checkbuffers(A)
 end
 
 ## similar
@@ -431,6 +441,7 @@ SparseMatrixCSC{Tv,Ti}(M::Transpose{<:Any,SparseMatrixCSC}) where {Tv,Ti} = Spar
 # converting from SparseMatrixCSC to other matrix types
 function Matrix(S::SparseMatrixCSC{Tv}) where Tv
     # Handle cases where zero(Tv) is not defined but the array is dense.
+    _checkbuffers(S)
     A = length(S) == nnz(S) ? Matrix{Tv}(undef, S.m, S.n) : zeros(Tv, S.m, S.n)
     for Sj in 1:S.n
         for Sk in nzrange(S, Sj)
@@ -800,6 +811,8 @@ respectively. Simultaneously fixes the one-position-forward shift in `X.colptr`.
 """
 @noinline function _distributevals_halfperm!(X::SparseMatrixCSC{Tv,Ti},
         A::SparseMatrixCSC{Tv,Ti}, q::AbstractVector{<:Integer}, f::Function) where {Tv,Ti}
+    resize!(X.rowval, nnz(A))
+    resize!(X.nzval, nnz(A))
     @inbounds for Xi in 1:A.n
         Aj = q[Xi]
         for Ak in nzrange(A, Aj)
@@ -836,11 +849,7 @@ transpose!(X::SparseMatrixCSC{Tv,Ti}, A::SparseMatrixCSC{Tv,Ti}) where {Tv,Ti} =
 adjoint!(X::SparseMatrixCSC{Tv,Ti}, A::SparseMatrixCSC{Tv,Ti}) where {Tv,Ti} = ftranspose!(X, A, conj)
 
 function ftranspose(A::SparseMatrixCSC{Tv,Ti}, f::Function) where {Tv,Ti}
-    X = SparseMatrixCSC(A.n, A.m,
-                        Vector{Ti}(undef, A.m+1),
-                        Vector{Ti}(undef, nnz(A)),
-                        Vector{Tv}(undef, nnz(A)))
-    halfperm!(X, A, 1:A.n, f)
+    halfperm!(sizehint!(spzeros(Tv, Ti, A.n, A.m), nnz(A)), A, 1:A.n, f)
 end
 adjoint(A::SparseMatrixCSC) = Adjoint(A)
 transpose(A::SparseMatrixCSC) = Transpose(A)
@@ -1055,10 +1064,7 @@ function permute!(X::SparseMatrixCSC{Tv,Ti}, A::SparseMatrixCSC{Tv,Ti},
         p::AbstractVector{<:Integer}, q::AbstractVector{<:Integer}) where {Tv,Ti}
     _checkargs_sourcecompatdest_permute!(A, X)
     _checkargs_sourcecompatperms_permute!(A, p, q)
-    C = SparseMatrixCSC(A.n, A.m,
-                        Vector{Ti}(undef, A.m + 1),
-                        Vector{Ti}(undef, nnz(A)),
-                        Vector{Tv}(undef, nnz(A)))
+    C = sizehint!(spzeros(Tv,Ti,A.n,A.m), nnz(A))
     _checkargs_permutationsvalid_permute!(p, C.colptr, q, X.colptr)
     unchecked_noalias_permute!(X, A, p, q, C)
 end
@@ -1074,10 +1080,7 @@ end
 function permute!(A::SparseMatrixCSC{Tv,Ti}, p::AbstractVector{<:Integer},
         q::AbstractVector{<:Integer}) where {Tv,Ti}
     _checkargs_sourcecompatperms_permute!(A, p, q)
-    C = SparseMatrixCSC(A.n, A.m,
-                        Vector{Ti}(undef, A.m + 1),
-                        Vector{Ti}(undef, nnz(A)),
-                        Vector{Tv}(undef, nnz(A)))
+    C = sizehint!(spzeros(Tv,Ti, A.n, A.m), nnz(A))
     workcolptr = Vector{Ti}(undef, A.n + 1)
     _checkargs_permutationsvalid_permute!(p, C.colptr, q, workcolptr)
     unchecked_aliasing_permute!(A, p, q, C, workcolptr)
@@ -1145,14 +1148,8 @@ julia> permute(A, [1, 2, 3, 4], [4, 3, 2, 1])
 function permute(A::SparseMatrixCSC{Tv,Ti}, p::AbstractVector{<:Integer},
         q::AbstractVector{<:Integer}) where {Tv,Ti}
     _checkargs_sourcecompatperms_permute!(A, p, q)
-    X = SparseMatrixCSC(A.m, A.n,
-                        Vector{Ti}(undef, A.n + 1),
-                        Vector{Ti}(undef, nnz(A)),
-                        Vector{Tv}(undef, nnz(A)))
-    C = SparseMatrixCSC(A.n, A.m,
-                        Vector{Ti}(undef, A.m + 1),
-                        Vector{Ti}(undef, nnz(A)),
-                        Vector{Tv}(undef, nnz(A)))
+    X = sizehint!(spzeros(Tv, Ti, A.m, A.n), nnz(A))
+    C = sizehint!(spzeros(Tv, Ti, A.n, A.m), nnz(A))
     _checkargs_permutationsvalid_permute!(p, C.colptr, q, X.colptr)
     unchecked_noalias_permute!(X, A, p, q, C)
 end
@@ -1246,6 +1243,7 @@ For an out-of-place version, see [`dropzeros`](@ref). For
 algorithmic information, see `fkeep!`.
 """
 dropzeros!(A::SparseMatrixCSC; trim::Bool = true) = fkeep!(A, (i, j, x) -> x != 0, trim)
+
 """
     dropzeros(A::SparseMatrixCSC; trim::Bool = true)
 
@@ -2214,7 +2212,7 @@ function permute_rows!(S::SparseMatrixCSC{Tv,Ti}, pI::Vector{Int}) where {Tv,Ti}
             k += 1
         end
     end
-    S
+    _checkbuffers(S)
 end
 
 function getindex_general(A::SparseMatrixCSC, I::AbstractVector, J::AbstractVector)
@@ -2351,6 +2349,7 @@ function Base.fill!(V::SubArray{Tv, <:Any, <:SparseMatrixCSC, Tuple{Vararg{Union
     else
         _spsetnz_setindex!(A, convert(Tv, x), I, J)
     end
+    _checkbuffers(A)
 end
 """
 Helper method for immediately preceding setindex! method. For all (i,j) such that i in I and
@@ -2630,7 +2629,7 @@ function setindex!(A::SparseMatrixCSC{Tv,Ti}, V::AbstractVecOrMat, Ix::Union{Int
     deleteat!(rowvalA, colptrA[end]:length(rowvalA))
     deleteat!(nzvalA, colptrA[end]:length(nzvalA))
 
-    return A
+    return _checkbuffers(A)
 end
 
 # Logical setindex!
@@ -2739,7 +2738,7 @@ function setindex!(A::SparseMatrixCSC, x::AbstractArray, I::AbstractMatrix{Bool}
             deleteat!(rowvalB, bidx:n)
         end
     end
-    A
+    _checkbuffers(A)
 end
 
 function setindex!(A::SparseMatrixCSC, x::AbstractArray, Ix::AbstractVector{<:Integer})
@@ -2850,7 +2849,7 @@ function setindex!(A::SparseMatrixCSC, x::AbstractArray, Ix::AbstractVector{<:In
             deleteat!(rowvalB, bidx:n)
         end
     end
-    A
+    _checkbuffers(A)
 end
 
 ## dropstored! methods
@@ -2885,7 +2884,7 @@ function dropstored!(A::SparseMatrixCSC, i::Integer, j::Integer)
             @inbounds A.colptr[m] -= 1
         end
     end
-    return A
+    return _checkbuffers(A)
 end
 """
     dropstored!(A::SparseMatrixCSC, I::AbstractVector{<:Integer}, J::AbstractVector{<:Integer})
@@ -2971,7 +2970,7 @@ function dropstored!(A::SparseMatrixCSC,
         deleteat!(rowvalA, rowidx:nnzA)
         deleteat!(nzvalA, rowidx:nnzA)
     end
-    return A
+    return _checkbuffers(A)
 end
 dropstored!(A::SparseMatrixCSC, i::Integer, J::AbstractVector{<:Integer}) = dropstored!(A, [i], J)
 dropstored!(A::SparseMatrixCSC, I::AbstractVector{<:Integer}, j::Integer) = dropstored!(A, I, [j])
@@ -3485,7 +3484,7 @@ function circshift!(O::SparseMatrixCSC, X::SparseMatrixCSC, (r,c)::Base.DimsInte
     @inbounds for i=1:O.n
         subvector_shifter!(O.rowval, O.nzval, O.colptr[i], O.colptr[i+1]-1, O.m, r)
     end
-    return O
+    return _checkbuffers(O)
 end
 
 circshift!(O::SparseMatrixCSC, X::SparseMatrixCSC, (r,)::Base.DimsInteger{1}) = circshift!(O, X, (r,0))
diff --git a/stdlib/SparseArrays/src/sparsevector.jl b/stdlib/SparseArrays/src/sparsevector.jl
index 8487cd5a4aab5..f5b1627430599 100644
--- a/stdlib/SparseArrays/src/sparsevector.jl
+++ b/stdlib/SparseArrays/src/sparsevector.jl
@@ -65,6 +65,13 @@ function nnz(x::SparseColumnView)
     return length(nzrange(parent(x), colidx))
 end
 
+
+function Base.sizehint!(v::SparseVector, newlen::Integer)
+    sizehint!(v.nzind, newlen)
+    sizehint!(v.nzval, newlen)
+    return v
+end
+
 ## similar
 #
 # parent method for similar that preserves stored-entry structure (for when new and old dims match)
diff --git a/stdlib/SparseArrays/test/sparse.jl b/stdlib/SparseArrays/test/sparse.jl
index df28e1aa0d6df..11e2f8b788630 100644
--- a/stdlib/SparseArrays/test/sparse.jl
+++ b/stdlib/SparseArrays/test/sparse.jl
@@ -25,7 +25,7 @@ end
     S = sparse(I, 3, 3)
     fill!(S, 0)
     @test iszero(S)  # test success with stored zeros via fill!
-    @test iszero(SparseMatrixCSC(2, 2, [1,2,3], [1,2], [0,0,1])) # test success with nonzeros beyond data range
+    @test_throws ArgumentError iszero(SparseMatrixCSC(2, 2, [1,2,3], [1,2], [0,0,1])) # test failure with nonzeros beyond data range
 end
 @testset "isone specialization for SparseMatrixCSC" begin
     @test isone(sparse(I, 3, 3))    # test success
@@ -2117,19 +2117,6 @@ end
     @test repr("text/plain", sparse([true true])) == "1×2 SparseArrays.SparseMatrixCSC{Bool,$Int} with 2 stored entries:\n  [1, 1]  =  1\n  [1, 2]  =  1"
 end
 
-@testset "check buffers" for n in 1:3
-    local A
-    rowval = [1,2,3]
-    nzval1  = Int[]
-    nzval2  = [1,1,1]
-    A = SparseMatrixCSC(n, n, [1:n+1;], rowval, nzval1)
-    @test nnz(A) == n
-    @test_throws BoundsError A[n,n]
-    A = SparseMatrixCSC(n, n, [1:n+1;], rowval, nzval2)
-    @test nnz(A) == n
-    @test A      == Matrix(I, n, n)
-end
-
 @testset "reverse search direction if step < 0 #21986" begin
     local A, B
     A = guardseed(1234) do
@@ -2231,8 +2218,6 @@ end
     # count should throw for sparse arrays for which zero(eltype) does not exist
     @test_throws MethodError count(SparseMatrixCSC(2, 2, Int[1, 2, 3], Int[1, 2], Any[true, true]))
     @test_throws MethodError count(SparseVector(2, Int[1], Any[true]))
-    # count should run only over S.nzval[1:nnz(S)], not S.nzval in full
-    @test count(SparseMatrixCSC(2, 2, Int[1, 2, 3], Int[1, 2], Bool[true, true, true])) == 2
 end
 
 @testset "sparse findprev/findnext operations" begin
@@ -2280,15 +2265,6 @@ end
     @test sum(s, dims=2) == reshape([1, 2, 3], 3, 1)
 end
 
-@testset "mapreduce of sparse matrices with trailing elements in nzval #26534" begin
-    B = SparseMatrixCSC{Int,Int}(2, 3,
-        [1, 3, 4, 5],
-        [1, 2, 1, 2, 999, 999, 999, 999],
-        [1, 2, 3, 6, 999, 999, 999, 999]
-    )
-    @test maximum(B) == 6
-end
-
 _length_or_count_or_five(::Colon) = 5
 _length_or_count_or_five(x::AbstractVector{Bool}) = count(x)
 _length_or_count_or_five(x) = length(x)