A few random stability/precompile improvements (#1030)

* migrate global -> Ref, should help type inference

* mark several definition checks with `@static`

* fix scoping issue with timeout definition

src/ConnectionPool.jl

@@ -452,26 +452,24 @@ end
 
 const nosslconfig = SSLConfig()
 const nosslcontext = Ref{OpenSSL.SSLContext}()
-default_sslconfig = nothing
-noverify_sslconfig = nothing
+const default_sslconfig = Ref{Union{Nothing, SSLConfig}}(nothing)
+const noverify_sslconfig = Ref{Union{Nothing, SSLConfig}}(nothing)
 
 function global_sslconfig(require_ssl_verification::Bool)::SSLConfig
-    global default_sslconfig
-    global noverify_sslconfig
-    if default_sslconfig === nothing
-        default_sslconfig = SSLConfig(true)
-        noverify_sslconfig = SSLConfig(false)
+    if default_sslconfig[] === nothing
+        default_sslconfig[] = SSLConfig(true)
+        noverify_sslconfig[] = SSLConfig(false)
     end
     if haskey(ENV, "HTTP_CA_BUNDLE")
-        MbedTLS.ca_chain!(default_sslconfig, MbedTLS.crt_parse(read(ENV["HTTP_CA_BUNDLE"], String)))
+        MbedTLS.ca_chain!(default_sslconfig[], MbedTLS.crt_parse(read(ENV["HTTP_CA_BUNDLE"], String)))
     elseif haskey(ENV, "CURL_CA_BUNDLE")
-        MbedTLS.ca_chain!(default_sslconfig, MbedTLS.crt_parse(read(ENV["CURL_CA_BUNDLE"], String)))
+        MbedTLS.ca_chain!(default_sslconfig[], MbedTLS.crt_parse(read(ENV["CURL_CA_BUNDLE"], String)))
     end
-    return require_ssl_verification ? default_sslconfig : noverify_sslconfig
+    return require_ssl_verification ? default_sslconfig[] : noverify_sslconfig[]
 end
 
 function global_sslcontext()::OpenSSL.SSLContext
-    if isdefined(OpenSSL, :ca_chain!)
+    @static if isdefined(OpenSSL, :ca_chain!)
         if haskey(ENV, "HTTP_CA_BUNDLE")
             sslcontext = OpenSSL.SSLContext(OpenSSL.TLSClientMethod())
             OpenSSL.ca_chain!(sslcontext, ENV["HTTP_CA_BUNDLE"])

src/IOExtras.jl

@@ -51,31 +51,31 @@ _doc = """
 
 Signal start/end of write or read operations.
 """
-if isdefined(Base, :startwrite)
+@static if isdefined(Base, :startwrite)
     "$_doc"
     Base.startwrite(io) = nothing
 else
     "$_doc"
     startwrite(io) = nothing
 end
 
-if isdefined(Base, :closewrite)
+@static if isdefined(Base, :closewrite)
     "$_doc"
     Base.closewrite(io) = nothing
 else
     "$_doc"
     closewrite(io) = nothing
 end
 
-if isdefined(Base, :startread)
+@static if isdefined(Base, :startread)
     "$_doc"
     Base.startread(io) = nothing
 else
     "$_doc"
     startread(io) = nothing
 end
 
-if isdefined(Base, :closeread)
+@static if isdefined(Base, :closeread)
     "$_doc"
     Base.closeread(io) = nothing
 else

src/Parsers.jl

@@ -351,7 +351,11 @@ const unhex = Int8[
 function __init__()
     # FIXME Consider turing off `PCRE.UTF` in `Regex.compile_options`
     # https://github.com/JuliaLang/julia/pull/26731#issuecomment-380676770
-    nt = isdefined(Base.Threads, :maxthreadid) ? Threads.maxthreadid() : Threads.nthreads()
+    nt = @static if isdefined(Base.Threads, :maxthreadid)
+        Threads.maxthreadid()
+    else
+        Threads.nthreads()
+    end
     resize!(empty!(status_line_regex),           nt)
     resize!(empty!(request_line_regex),          nt)
     resize!(empty!(header_field_regex),          nt)

src/Servers.jl

@@ -410,8 +410,8 @@ After `reuse_limit + 1` transactions, signal `final_transaction` to the
 transaction handler, which will close the connection.
 """
 function handle_connection(f, c::Connection, listener, readtimeout, access_log)
+    wait_for_timeout = Ref{Bool}(true)
     if readtimeout > 0
-        wait_for_timeout = Ref{Bool}(true)
         @async check_readtimeout(c, readtimeout, wait_for_timeout)
     end
     try