https://github.com/libjpeg-turbo/libjpeg-turbo/issues/705
https://github.com/libjpeg-turbo/libjpeg-turbo/commit/035ea386d1b6a99a8a1e2ab57cc1fc903569136c

From 035ea386d1b6a99a8a1e2ab57cc1fc903569136c Mon Sep 17 00:00:00 2001
From: DRC <information@libjpeg-turbo.org>
Date: Thu, 6 Jul 2023 12:04:22 -0400
Subject: [PATCH] Build: Fix regression test concurrency issues

- The example-*bit-*-decompress test must run after the
  example-*bit-*-compress test, since the latter generates
  testout*-example.jpg.

- Add -static to the filenames of all output files generated by the
  "static" regression tests, to avoid conflicts with the "shared"
  regression tests.

- Add the PID to the filenames of all files generated by the tjunittest
  packed-pixel image I/O tests.

- Check the return value of MD5File() in tjunittest to avoid a segfault
  if the file doesn't exist.  (Prior to the fix described above, that
  could occur if two instances of tjunittest ran concurrently from the
  same directory with the same -bmp and -precision arguments.)

Fixes #705
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1004,7 +1004,7 @@ foreach(libtype ${TEST_LIBTYPES})
 
       if(sample_bits EQUAL 12)
         set(tjbench tjbench12)
-        set(testout testout12)
+        set(testout testout12${suffix})
 
         set(MD5_PPM_GRAY_TILE 2f799249148b1a9d0e61fa4408f6c397)
         set(MD5_PPM_420_8x8_TILE b25684e1af37be504ee3fd137757353f)
@@ -1024,7 +1024,7 @@ foreach(libtype ${TEST_LIBTYPES})
         set(MD5_PPM_444_TILE 2f571a032e4dbc8ef40f75219d336b0b)
       else()
         set(tjbench tjbench)
-        set(testout testout)
+        set(testout testout${suffix})
 
         set(MD5_PPM_GRAY_TILE 2c3b567086e6ca0c5e6d34ad8d6f6fe8)
         set(MD5_PPM_420_8x8_TILE efca1bdf0226df01777137778cf986ec)
@@ -1160,7 +1160,7 @@ foreach(libtype ${TEST_LIBTYPES})
       set(cjpeg cjpeg12)
       set(djpeg djpeg12)
       set(jpegtran jpegtran12)
-      set(testout testout12)
+      set(testout testout12${suffix})
 
       set(TESTORIG testorig12.jpg)
       set(MD5_JPEG_RGB_ISLOW 9d7369207c520d37f2c1cbfcb82b2964)
@@ -1222,7 +1222,7 @@ foreach(libtype ${TEST_LIBTYPES})
       set(cjpeg cjpeg)
       set(djpeg djpeg)
       set(jpegtran jpegtran)
-      set(testout testout)
+      set(testout testout${suffix})
 
       set(TESTORIG testorig.jpg)
       set(MD5_JPEG_RGB_ISLOW 1d44a406f61da743b5fd31c0a9abdca3)
@@ -1632,6 +1632,8 @@ foreach(libtype ${TEST_LIBTYPES})
     add_test(example-${sample_bits}bit-${libtype}-decompress
       ${CMAKE_CROSSCOMPILING_EMULATOR} example${suffix} decompress
         ${EXAMPLE_12BIT_ARG} ${testout}-example.jpg ${testout}-example.ppm)
+    set_tests_properties(example-${sample_bits}bit-${libtype}-decompress
+      PROPERTIES DEPENDS example-${sample_bits}bit-${libtype}-compress)
     add_test(example-${sample_bits}bit-${libtype}-decompress-cmp
       ${CMAKE_CROSSCOMPILING_EMULATOR} ${MD5CMP} ${MD5_PPM_EXAMPLE_DECOMPRESS}
         ${testout}-example.ppm)
--- a/tjunittest.c
+++ b/tjunittest.c
@@ -977,8 +977,8 @@ static int doBmpTest(const char *ext, int width, int align, int height, int pf,
     THROW("Could not allocate memory");
   initBitmap(buf, width, pitch, height, pf, bottomUp);
 
-  SNPRINTF(filename, 80, "test_bmp%d_%s_%d_%s.%s", precision, pixFormatStr[pf],
-           align, bottomUp ? "bu" : "td", ext);
+  SNPRINTF(filename, 80, "test_bmp%d_%s_%d_%s_%d.%s", precision, pixFormatStr[pf],
+           align, bottomUp ? "bu" : "td", getpid(), ext);
   if (precision == 8) {
     TRY_TJ(handle, tj3SaveImage8(handle, filename, (unsigned char *)buf, width,
                                  pitch, height, pf));
@@ -990,6 +990,10 @@ static int doBmpTest(const char *ext, int width, int align, int height, int pf,
                                   width, pitch, height, pf));
   }
   md5sum = MD5File(filename, md5buf);
+  if (!md5sum) {
+    printf("\n   Could not determine MD5 sum of %s\n", filename);
+    retval = -1;  goto bailout;
+  }
   if (strcasecmp(md5sum, md5ref))
     THROW_MD5(filename, md5sum, md5ref);