Re: weird desktop.el change

[Markus Triska]

Richard Stallman <address@hidden> writes:

> I think it would be better to implement this warning in the code
> generation stage so as to give the warning the correct line number.

I will revisit this issue after the release. For now, I compiled a
list of all opportunities for this optimisation in Emacs trunk, found
with the following change to bytecomp.el. It only emits a warning and
does not change the byte code. Most line numbers are accurate; in some
cases they may point to the wrong `mapcar' call though.

*** bytecomp.el 11 Apr 2007 12:56:05 +0200      2.198
--- bytecomp.el 15 Apr 2007 00:18:34 +0200      
***************
*** 2831,2836 ****
--- 2831,2839 ----
  (defun byte-compile-normal-call (form)
    (if byte-compile-generate-call-tree
        (byte-compile-annotate-call-tree form))
+   (when (and for-effect (eq (car form) 'mapcar))
+     (byte-compile-set-symbol-position 'mapcar)
+     (byte-compile-warn "`mapcar' called for effect; use `mapc' instead"))
    (byte-compile-push-constant (car form))
    (mapc 'byte-compile-form (cdr form))        ; wasteful, but faster.
    (byte-compile-out 'byte-call (length (cdr form))))


File                    Line(s)
==================      ==================

byte-opt.el             1999
bytecomp.el             4239
cc-mode.el              850,1439
allout.el               1133,5465
ansi-color.el           567,571,580
autoinsert.el           275
bookmark.el             1572,1789
desktop.el              871,1031
dired-aux.el            1335
dired.el                3326
ediff-diff.el           351,361,364
ediff-mult.el           639,924,1308,1369,1369
ediff-ptch.el           338,335
ediff-util.el           1320,1344,2442,2445,3746
emerge.el               1889
ffap.el                 485
filecache.el            287,389,405,446,459,722,771
files.el                646
find-lisp.el            273
finder.el               137
follow.el               394,400
frame.el                453,832
help.el                 335
hi-lock.el              490
ido.el                  3357,3606,3654
jka-cmpr-hook.el        100
printing.el             5293,5323
ps-print.el             5020,5662,6435,6437,6436,6437
simple.el               5370
startup.el              977
tempo.el                318,463,559,578
tumme.el                825,902,2148
vc-hooks.el             354
vc.el                   1599,1622,1666,2289,2622,2650
woman.el                1537
calc-ext.el             621,655,1280
calc-help.el            422,441
calc-misc.el            148
calc-store.el           175,178
calc-stuff.el           194
calc-units.el           673
calc.el                 921,978,978,987,1012,1060,1082,1183,1187,1366
hilit19.el              668,978,1026
emacsbug.el             152
feedmail.el             1591,1838
reporter.el             255
rmail.el                1457
supercite.el            1046,1057,1067
authors.el              669
cl.el                   596,641
cust-print.el           247,262,276
disass.el               253
easy-mmode.el           458
edebug.el               4424
elint.el                221,545,569,668,770
elp.el                  618
generic.el              208
re-builder.el           518
regi.el                 169
sregex.el               568
solitaire.el            403,449
zone.el                 401
icalendar.el            1534,1640
gnus-agent.el           686,1004,1278,2038,2091,2096,3487
gnus-art.el             3753,7273
gnus-diary.el           311
gnus-group.el           1629,2204,2405,4107
gnus-int.el             169,199,229,285,292,299,306,316,334,344,404,513,
                               534,584,642,688
gnus-msg.el             1577,1578,1584
gnus-nocem.el           194
gnus-registry.el        352
gnus-spec.el            300
gnus-srvr.el            395,505,525,537,553,577,580,629,785,1006
gnus-start.el           968,1466,1475,1781,3026
gnus-sum.el             1482,1566,4132,5847,9275,10470,11286
gnus-topic.el           247,354,1300,1321
gnus.el                 2740,3522
imap.el                 1032,1031,2743
legacy-gnus-agent.el    114,130
message.el              7056
mm-util.el              33,983,1066
mml.el                  157,652,813
nndiary.el              1699
nnfolder.el             1200
nnimap.el               823,1145,1210,1561,1565,1654
nnmail.el               1675
nnmaildir.el            242,710,740,760,759,824,821,860,928,936,1090,1147,
                               1540,1544,1548,1584,1593,1611
nnml.el                 945
nnvirtual.el            342,679,738
nnweb.el                557
sieve-manage.el         375
webmail.el              199
artist.el               1565,1614,1703,1740,3163,3223,3225,3362,5364
flyspell.el             613,632
org.el                  11856,17011,17071,17477
reftex-cite.el          712,957
reftex-ref.el           670
reftex-sel.el           424,646
reftex-toc.el           619
reftex.el               862,1344
table.el                1379,1412,1446,1472,1651,3144,3226,3923,3925,4095
ethio-util.el           1064
mule-diag.el            842
erc-backend.el          658
erc-track.el            672
url-dav.el              936
url-vars.el             65
cua-rect.el             734,840,1404
viper-keym.el           173,213
viper-macs.el           661,665,673,680
viper-util.el           1265
viper.el                795
sun-mouse.el            504
tvi970.el               40
w32-win.el              114
ange-ftp.el             4558,6033
eudc-hotlist.el         72,84
eudc.el                 510,515,543,568,574,644,991,998
eudcb-bbdb.el           78,206
eudcb-ldap.el           133
tramp-vc.el             103
tramp.el                3976,4635,4747,5253
ada-mode.el             1434,1439
ada-prj.el              257,258
cc-styles.el            384,639
cperl-mode.el           1103,5533,7140,7264,7273,7273,7339,7345,7363,7353,7360
delphi.el               1689,1692,1724,1891,1912,1984
ebnf-yac.el             281,278
ebnf2ps.el              4654,5141
ebrowse.el              1151,1641,2259,4151,4166
f90.el                  685
fortran.el              615
idlw-shell.el           3481,3481,4533
idlw-toolbar.el         914,945
idlwave.el              2828,2830,4243,5561,5605,6320,6336,6808,7552,8278,8438
sh-script.el            1892,1899
sql.el                  866
vhdl-mode.el            2814,5299,7148
xscheme.el              104