Add corner-cases tests for manually constructed profiles; ensure we c…

…atch every sample

Fix the bugs in handling those cases :)

src/PProf.jl

@@ -154,11 +154,19 @@ function pprof(data::Union{Nothing, Vector{UInt}} = nothing,
         1,      # events
     ]
 
-    lastwaszero = false  # (Legacy: used when has_meta = false)
-
+    lastwaszero = true  # (Legacy: used when has_meta = false)
+
+    # The Profile data buffer is a big array, with each sample appended one after the other.
+    # Each sample now looks like this:
+    # | ip | ip | ip | meta1 | meta2 | meta3 | meta4| 0x0 | 0x0 |
+    # We iterate backwards, starting from the end, so that we don't encounter the metadata
+    # and mistake it for more ip addresses. For each sample, we skip the zeros, consume the
+    # metadata, then continue scanning the ip addresses, and when we hit another end of a
+    # block, we finish the sample we just consumed.
     idx = length(data)
     meta = nothing
     while idx > 0
+        # We handle the very first sample after the loop.
         if has_meta && Profile.is_block_end(data, idx)
             if meta !== nothing
                 # Finish last block
@@ -181,7 +189,7 @@ function pprof(data::Union{Nothing, Vector{UInt}} = nothing,
             ]
             idx -= (Profile.nmeta + 2)  # skip all the metas, plus the 2 nulls that end a block.
             continue
-        elseif !has_meta && idx != length(data) && data[idx] == 0
+        elseif !has_meta && data[idx] == 0
             # Avoid creating empty samples
             # ip == 0x0 is the sentinel value for finishing a backtrace (when meta is disabled), therefore finising a sample
             # On some platforms, we sometimes get two 0s in a row for some reason...
@@ -278,6 +286,15 @@ function pprof(data::Union{Nothing, Vector{UInt}} = nothing,
             push!(location_id, ip)
         end
     end
+    if length(data) > 0
+        # Finish the very last sample
+        if has_meta
+            push!(samples, Sample(;location_id = reverse!(location_id), value = value, label = meta))
+        else
+            push!(samples, Sample(;location_id = reverse!(location_id), value = value))
+        end
+        location_id = Vector{eltype(data)}()
+    end
 
     # If from_c=false funcs and locs should NOT contain C functions
     prof = PProfile(

test/PProf.jl

@@ -65,6 +65,40 @@ function load_prof_proto(file)
     open(io->decode(ProtoDecoder(GzipDecompressorStream(io)), PProf.perftools.profiles.Profile), file, "r")
 end
 
+@testset "Corner Cases" begin
+    @testset "non-meta profile" begin
+
+        @testset "0 sample profile" begin
+            prof = load_prof_proto(pprof(UInt64[], out=tempname(), web=false))
+            @test length(prof.sample) == 0
+        end
+        @testset "1 sample profile" begin
+            prof = load_prof_proto(pprof(UInt64[0xdeadbeef,0], out=tempname(), web=false))
+            @test length(prof.sample) == 1
+        end
+
+        @testset "2 sample, 1 location profile" begin
+            prof = load_prof_proto(pprof(UInt64[0xdeadbeef,0, 0xdeadbeef, 0], out=tempname(), web=false))
+            @test length(prof.sample) == 2
+            @test length(prof.location) == 1
+        end
+    end
+    @testset "with-meta profile" begin
+        @testset "1 sample profile" begin
+            data = UInt64[0xdeadbeef, 1, 1, 1, 1, 0, 0]
+            prof = load_prof_proto(pprof(data, out=tempname(), web=false))
+            @test length(prof.sample) == 1
+        end
+
+        @testset "2 sample 1 location profile" begin
+            data = UInt64[0xdeadbeef, 1, 1, 1, 1, 0, 0, 0xdeadbeef, 1, 1, 1, 1, 0, 0]
+            prof = load_prof_proto(pprof(data, out=tempname(), web=false))
+            @test length(prof.sample) == 2
+            @test length(prof.location) == 1
+        end
+    end
+end
+
 @testset "with_c" begin
     Profile.clear()