Use temporary directory more effectively (#34)

* put smt2 files in temp dir

Now that we have a proper per-run temp directory, we can put
generated smt2 files in the temp directory, so that the files do not
clutter the main temp directory, and so that the files will be
cleaned up when Picus finishes execution.

* feat: add --noclean to prevent cleaning

Picus initially never clean up temporary files. However, the last commit
changed this so that temporary files are cleaned up. Sometimes, though,
we really do not want to clean up files (e.g. in order to generate
smt2 files for debugging purposes). This commit adds the flag to
control whether to run the clean up.

picus.rkt

@@ -7,6 +7,7 @@
          (prefix-in r1cs: "./picus/r1cs/r1cs-grammar.rkt")
          (prefix-in dpvl: "./picus/algorithms/dpvl.rkt")
          (prefix-in pre: "./picus/precondition.rkt")
+         "picus/tmpdir.rkt"
          "ansi.rkt"
          "verbose.rkt")
 
@@ -17,6 +18,7 @@
 (define arg-r1cs #f)
 (define arg-circom #f)
 (define arg-opt-level #f)
+(define arg-clean? #t)
 (define arg-timeout 5000)
 (define arg-solver "z3")
 (define arg-selector "counter")
@@ -37,6 +39,8 @@
                (when (not (string-suffix? arg-circom ".circom"))
                  (tokamak:exit "file needs to be *.circom"))]
  #:once-each
+ [("--noclean") "do not clean up temporary files (default: false)"
+                (set! arg-clean? #f)]
  [("--opt-level") p-opt-level "optimization level for circom compilation (only applicable for --circom, default: 0)"
                   (set! arg-opt-level
                         (match p-opt-level
@@ -85,16 +89,10 @@
 (unless (implies arg-opt-level arg-circom)
   (tokamak:exit "optimization level only applicable for --circom"))
 
-;; invariant: tmpdir = #f iff arg-circom = #f
-(define tmpdir
-  (cond
-    [arg-circom (make-temporary-directory "picus~a")]
-    [else #f]))
-
 (when arg-circom
   (unless (system* (find-executable-path "circom")
                    "-o"
-                   tmpdir
+                   (get-tmpdir)
                    "--r1cs"
                    arg-circom
                    "--sym"
@@ -103,16 +101,9 @@
                      ["1" "--O1"]
                      ["2" "--O2"]))
     (tokamak:exit "circom compilation failed"))
-  (set! arg-r1cs (~a (build-path tmpdir (file-name-from-path (path-replace-extension arg-circom ".r1cs"))))))
-
-;; NOTE: we intentionally do not use call this function within
-;; dynamic-wind (i.e. try-finally) so that if the program crashes
-;; we can still inspect the temporary directory,
-;; although cleaning up the temporary directory in such case is now
-;; a responsibility of the user.
-(define (clean-tmpdir!)
-  (when arg-circom
-    (delete-directory/files tmpdir)))
+  (set! arg-r1cs (~a (build-path (get-tmpdir)
+                                 (file-name-from-path
+                                  (path-replace-extension arg-circom ".r1cs"))))))
 
 (printf "# r1cs file: ~a\n" arg-r1cs)
 (printf "# timeout: ~a\n" arg-timeout)
@@ -246,4 +237,5 @@
   (when (> arg-cex-verbose 0)
     (format-cex "other bindings" (order other-info))))
 
-(clean-tmpdir!)
+(when arg-clean?
+  (clean-tmpdir!))

picus/solvers/common.rkt

@@ -5,17 +5,17 @@
          racket/port
          racket/match
          racket/engine
+         racket/file
          (prefix-in tokamak: "../tokamak.rkt")
-         (prefix-in config: "../config.rkt"))
+         (prefix-in config: "../config.rkt")
+         "../tmpdir.rkt")
 
 (define ((make-solve #:executable executable
                      #:options [options '()])
          smt-str timeout #:verbose? [verbose? #f] #:output-smt? [output-smt? #f])
-  (define temp-folder (find-system-path 'temp-dir))
-  (define temp-file (format "picus~a.smt2"
-                            (string-replace (format "~a" (current-inexact-milliseconds)) "." "")))
-  (define temp-path (build-path temp-folder temp-file))
+  (define temp-path (make-temporary-file "picus~a.smt2" #:base-dir (get-tmpdir)))
   (with-output-to-file temp-path
+    #:exists 'replace
     (λ () (display smt-str)))
   (when (or verbose? output-smt?)
     (printf "(written to: ~a)\n" temp-path))

picus/tmpdir.rkt

@@ -0,0 +1,15 @@
+#lang racket/base
+
+(provide get-tmpdir
+         clean-tmpdir!)
+(require racket/file)
+
+(define tmpdir #f)
+
+(define (get-tmpdir)
+  (unless tmpdir
+    (set! tmpdir (make-temporary-directory "picus~a")))
+  tmpdir)
+
+(define (clean-tmpdir!)
+  (delete-directory/files tmpdir #:must-exist? #f))