common/234: avoid intermittent failure by dynamic path length generation

test cases/common/234 very long commmand line/codegen.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 
 import sys
+from pathlib import Path
 
-with open(sys.argv[2], 'w') as f:
-    print('int func{n}(void) {{ return {n}; }}'.format(n=sys.argv[1]), file=f)
+Path(sys.argv[2]).write_text(
+    'int func{n}(void) {{ return {n}; }}'.format(n=sys.argv[1]))

test cases/common/234 very long commmand line/main.c

@@ -1,5 +1 @@
-int main(int argc, char **argv) {
-  (void) argc;
-  (void) argv;
-  return 0;
-}
+int main(void) { return 0; }

test cases/common/234 very long commmand line/meson.build

@@ -6,6 +6,10 @@ if build_machine.system() == 'windows'
   # cmd.exe: 8kb
   # CreateProcess: 32kb
   limit = 32767
+  # NOTE: filename limit is 260 characters unless
+  # 1. Python >= 3.6 is being used
+  # 2. Windows 10 registry has been edited to enable long pathnaems
+  # ninja backend uses absolute filenames, so we ensure they don't exceed 260.
 elif build_machine.system() == 'cygwin'
   # cygwin-to-win32: see above
   # cygwin-to-cygwin: no limit?
@@ -18,20 +22,21 @@ else
   limit = 131072
 endif
 # Now exceed that limit, but not so far that the test takes too long.
-name = 'ALongFilenameMuchLongerThanIsNormallySeenAndReallyHardToReadThroughToTheEndAMooseOnceBitMySisterSheNowWorksAtLLamaFreshFarmsThisHasToBeSoLongThatWeExceed128KBWithoutCompilingTooManyFiles'
-namelen = 187
+namelen = 260
 nfiles = 50 + limit / namelen
 message('Expected link commandline length is approximately ' + '@0@'.format((nfiles * (namelen+28))))
 
-seq = run_command('seq.py', '1', '@0@'.format(nfiles)).stdout().strip().split('\n')
+seq = run_command('name_gen.py', nfiles.to_string(), meson.build_root()).stdout().strip().split('\n')
 
 sources = []
 codegen = find_program('codegen.py')
 
-foreach i : seq
-  sources += custom_target('codegen' + i,
-                           command: [codegen, i, '@OUTPUT@'],
-                           output: name + i + '.c')
+i=0
+foreach name : seq
+  sources += custom_target('codegen' + i.to_string(),
+                           command: [codegen, i.to_string(), '@OUTPUT@'],
+                           output: name + '.c')
+  i+=1
 endforeach
 
 shared_library('sharedlib', sources)

test cases/common/234 very long commmand line/name_gen.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+"""
+generate sequence of filename that does not exceed MAX_LEN=260
+for Python < 3.6 and Windows without modified registry
+"""
+
+import sys
+import string
+
+name_len = 260 - len(sys.argv[2]) - 4 - 39 - 4 - 2
+if name_len < 1:
+    raise ValueError('The meson build directory pathname is so long '
+                     'that we cannot generate filenames within 260 characters.')
+# leave room for suffix and file separators, and meson generated text
+# e.g. ".c.obj.d" and other decorators added by Meson at configuration
+# for intermediate files
+
+base = string.ascii_letters * 5  # 260 characters
+max_num_len = len(str(sys.argv[1]))
+base = base[: name_len - max_num_len]
+
+for i in range(int(sys.argv[1])):
+    print("{base}{i:0{max_num_len}d}".format(base=base, max_num_len=max_num_len, i=i))