[Bug testsuite/70516] [4.9/5/6 Regression] Regtesting acats hangs on x86_64-apple-darwin15.4

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70516

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
> Can you bisect it?  There aren't that many changes that could affect
> anything at all.

The problem is non-deterministic: it occurs less than once every two tests. So
r234234 is the first revision for which I saw it, but it does not mean that it
could not have occurred before it. The main change in the reported range was
the update of Tcl to 8.6 from 8.5, but it does not seem to be the culprit.

> Any Ada processes (compiler or some testcase) hang?

AFAICT no, but there is at least one expect process hanging. If I kill it,
regtesting completes after eventually running some gnat tests. Before killing
the expect process I see

[Book15] gcc/build_c% lf gcc/testsuite/ada/acats-parallel/
1/    108/  117/  126/  135/  144/  153/  162/  171/  180/  19/   199/  207/ 
216/  225/  25/  34/  43/  52/  61/  70/  8/   89/  98/
10/   109/  118/  127/  136/  145/  154/  163/  172/  181/  190/  2/    208/ 
217/  226/  26/  35/  44/  53/  62/  71/  80/  9/   99/
100/  11/   119/  128/  137/  146/  155/  164/  173/  182/  191/  20/   209/ 
218/  227/  27/  36/  45/  54/  63/  72/  81/  90/  finished
101/  110/  12/   129/  138/  147/  156/  165/  174/  183/  192/  200/  21/  
219/  228/  28/  37/  46/  55/  64/  73/  82/  91/
102/  111/  120/  13/   139/  148/  157/  166/  175/  184/  193/  201/  210/ 
22/   229/  29/  38/  47/  56/  65/  74/  83/  92/
103/  112/  121/  130/  14/   149/  158/  167/  176/  185/  194/  202/  211/ 
220/  23/   3/   39/  48/  57/  66/  75/  84/  93/
104/  113/  122/  131/  140/  15/   159/  168/  177/  186/  195/  203/  212/ 
221/  230/  30/  4/   49/  58/  67/  76/  85/  94/
105/  114/  123/  132/  141/  150/  16/   169/  178/  187/  196/  204/  213/ 
222/  231/  31/  40/  5/   59/  68/  77/  86/  95/
106/  115/  124/  133/  142/  151/  160/  17/   179/  188/  197/  205/  214/ 
223/  232/  32/  41/  50/  6/   69/  78/  87/  96/
107/  116/  125/  134/  143/  152/  161/  170/  18/   189/  198/  206/  215/ 
224/  24/   33/  42/  51/  60/  7/   79/  88/  97/

after killing it, the gcc/testsuite/ada/acats-parallel directory is gone.

Killing the last make gives something such as

/opt/gcc/logs/check_a-234697p25.log:/bin/sh: line 30:  3681 Killed: 9          
    make check-acats1 check-acats2 check-acats3 check-acats4 check-acats5
check-acats6 check-acats7 check-acats8 check-acats9 check-acats10 check-acats11
check-acats12 check-acats13 check-acats14 check-acats15 check-acats16
check-acats17 check-acats18 check-acats19 check-acats20 check-acats21
check-acats22 check-acats23 check-acats24 check-acats25 check-acats26
check-acats27 check-acats28 check-acats29 check-acats30 check-acats31
check-acats32 check-acats33 check-acats34 check-acats35 check-acats36
check-acats37 check-acats38 check-acats39 check-acats40 check-acats41
check-acats42 check-acats43 check-acats44 check-acats45 check-acats46
check-acats47 check-acats48 check-acats49 check-acats50 check-acats51
check-acats52 check-acats53 check-acats54 check-acats55 check-acats56
check-acats57 check-acats58 check-acats59 check-acats60 check-acats61
check-acats62 check-acats63 check-acats64 check-acats65 check-acats66
check-acats67 check-acats68 check-acats69 check-acats70 check-acats71
check-acats72 check-acats73 check-acats74 check-acats75 check-acats76
check-acats77 check-acats78 check-acats79 check-acats80 check-acats81
check-acats82 check-acats83 check-acats84 check-acats85 check-acats86
check-acats87 check-acats88 check-acats89 check-acats90 check-acats91
check-acats92 check-acats93 check-acats94 check-acats95 check-acats96
check-acats97 check-acats98 check-acats99 check-acats100 check-acats101
check-acats102 check-acats103 check-acats104 check-acats105 check-acats106
check-acats107 check-acats108 check-acats109 check-acats110 check-acats111
check-acats112 check-acats113 check-acats114 check-acats115 check-acats116
check-acats117 check-acats118 check-acats119 check-acats120 check-acats121
check-acats122 check-acats123 check-acats124 check-acats125 check-acats126
check-acats127 check-acats128