Add do-block support for dlopen()

NEWS.md

@@ -30,6 +30,10 @@ Standard library changes
  (environment, flags, working directory, etc) if `x` is the first interpolant and errors
  otherwise ([#24353]).
 
+#### Libdl
+
+* `dlopen()` can now be invoked in `do`-block syntax, similar to `open()`.
+
 #### LinearAlgebra
 
 * The BLAS submodule no longer exports `dot`, which conflicts with that in LinearAlgebra ([#31838]).

stdlib/Libdl/src/Libdl.jl

@@ -113,6 +113,33 @@ function dlopen(s::AbstractString, flags::Integer = RTLD_LAZY | RTLD_DEEPBIND; t
  return ret
 end
 
+"""
+ dlopen(f::Function, args...; kwargs...)
+
+Wrapper for usage with `do` blocks to automatically close the dynamic library once
+control flow leaves the `do` block scope.
+
+# Example
+```julia
+vendor = dlopen("libblas") do lib
+ if Libdl.dlsym(lib, :openblas_set_num_threads; throw_error=false) !== nothing
+ return :openblas
+ else
+ return :other
+ end
+end
+```
+"""
+function dlopen(f::Function, args...; kwargs...)
+ hdl = nothing
+ try
+ hdl = dlopen(args...; kwargs...)
+ f(hdl)
+ finally
+ dlclose(hdl)
+ end
+end
+
 """
  dlopen_e(libfile::AbstractString [, flags::Integer])
 

stdlib/Libdl/test/runtests.jl

@@ -196,6 +196,18 @@ let dl = C_NULL
  end
 end
 
+# test do-block dlopen
+Libdl.dlopen(abspath(joinpath(private_libdir, "libccalltest"))) do dl
+ fptr = Libdl.dlsym(dl, :set_verbose)
+ @test fptr !== nothing
+ @test_throws ErrorException Libdl.dlsym(dl, :foo)
+
+ fptr = Libdl.dlsym_e(dl, :set_verbose)
+ @test fptr != C_NULL
+ fptr = Libdl.dlsym_e(dl, :foo)
+ @test fptr == C_NULL
+end
+
 # test dlclose
 # If dl is NULL, jl_dlclose should return -1 and dlclose should return false
 # dlclose should return true on success and false on failure