# Thought: saving users from themselves in macros that explode **URL:** \ **Category:** compiler\ **Created:** [July 8, 2018, 5:26pm UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907 "2018-07-08T17:26:00Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![ExpHP](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/exphp/32/6208_2.png) [@ExpHP](https://internals.rust-lang.org/u/ExpHP)\ **Post date:** [July 8, 2018, 5:26pm UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/1 "2018-07-08T17:26:00Z")
**You do NOT want to attempt to compile the following snippet:** ```rust macro_rules! blowup { ([$($t:tt)+]) => { blowup!{[$($t:tt)+]} }; // note the :tt ! } fn main() { blowup!([a]); } ``` (note: the brackets are only there to work around a bug fixed in #52145 which slows down the parsing of `$($t:tt)+`) If you try to build this and are on linux with a reasonably-sized swap partition, you are very likely to send yourself into complete and utter turmoil. You've probably experienced this before doing something else similarly dumb: - The program eventually requires so much memory (and is using it so actively) that memory for other absolutely essential things (like your window manager) are paged out to swap, causing your system to stop responding. - Soon, the program requires so much memory that not _even all of its own memory_ can fit in physical memory. The program's execution is slowed down so much by constant page faults that it can't even reach the point where it would OOM. - ...so basically you find yourself with a very warm brick for a few hours (or until you shut it off). The prevailing philosophy in most circles is: > Well, then _don't do that!_ but you know as well as I know that these things do not usually happen on purpose! * * * So maybe the compiler can help. Mind, we don't have to solve the halting problem, all we need here is bang-for-the-buck; we want to head-off common deadly mistakes, like an extra `:tt` in an incremental muncher. Rust already has a `#[recursion_limit]` to help combat some forms of rogue macros, but it doesn't help much with the above example. #### A strawman proposal @limira in [this comment on #51754](https://github.com/rust-lang/rust/issues/51754#issuecomment-403295118) suggests the following: > 1. Define a constant (like `recursion_limit`), maybe its name is: `max_macro_grow_factor = 1024`. > 2. Record the first number of tokens: `n` > 3. At each recursive call, check the new number of tokens: `m` > 4. If m \> `n * max_macro_grow_factor` then > > - stop the macro-expansion process > - report error to user > - suggest them to check the involving rules > - suggest them to increase `max_macro_grow_factor = 2048` if they are sure there is no problem with their macro. I'm going to push this forward as a starter for discussion. I don't think that this _precisely_ is the way to go, as there are subtleties like - what if a macro has no tokens as input? - it is common for macros that take small inputs to expand to very large outputs composed largely of fixed tokens - what about backwards compatibility? Is there a reasonable default factor we can pick such that no existing legitimately-working macro is liable to exceed it? so I'm opening this thread as a place to toss around ideas. Any thoughts? ---
**Author:** ![Soni](https://avatars.discourse-cdn.com/v4/letter/s/a3d4f5/32.png) [@Soni](https://internals.rust-lang.org/u/Soni)\ **Post date:** [July 8, 2018, 7:00pm UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/2 "2018-07-08T19:00:14Z")
Set a memory limit? ---
**Author:** ![mark-i-m](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/mark-i-m/32/3167_2.png) [@mark-i-m](https://internals.rust-lang.org/u/mark-i-m)\ **Post date:** [July 8, 2018, 9:35pm UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/3 "2018-07-08T21:35:03Z")
It would be nice if the limit was program-dependant, rather than platform dependant. That’s my problem with memory limits. In general, I believe NFA regex parsers can explore an exponential number of pathes. Depending on the order of exploring paths, I think we could end up using exponential space in our macros parser (it’s basically a breath first search). We could switch to something like depth-first search. Then you would only use linear memory and would just run into the recursion limit, right? On the other hand, we have the normal problems with DFS… ---
**Author:** ![ExpHP](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/exphp/32/6208_2.png) [@ExpHP](https://internals.rust-lang.org/u/ExpHP)\ **Post date:** [July 8, 2018, 10:08pm UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/4 "2018-07-08T22:08:32Z")
This however is not a problem of exponential solution space. Each time `blowup!` expands it takes time and memory that is linear in the input; but the _input itself_ grows exponentially with each call. (but geeze, I wonder… are there pathological macros out there that the macro parser generates an exponential number of paths for? ISTM that the parser is too averse to ambiguities for this to actually occur) ---
**Author:** ![untitaker](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/untitaker/32/8846_2.png) [@untitaker](https://internals.rust-lang.org/u/untitaker)\ **Post date:** [July 9, 2018, 8:13pm UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/5 "2018-07-09T20:13:30Z")
Would this be prevented by setting a maximum length of the macro input? One of the recursive calls would probably fail then. I don’t really see why we need to compute a growth rate etc instead of having a static limit. ---
**Author:** ![mark-i-m](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/mark-i-m/32/3167_2.png) [@mark-i-m](https://internals.rust-lang.org/u/mark-i-m)\ **Post date:** [July 10, 2018, 2:44am UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/6 "2018-07-10T02:44:12Z")
I would still rather the limit be program dependant. ---
**Author:** ![g6D2ZTB](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/g6d2ztb/32/6177_2.png) [@g6D2ZTB](https://internals.rust-lang.org/u/g6D2ZTB)\ **Post date:** [January 17, 2019, 10:44am UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/7 "2019-01-17T10:44:09Z")
> [@ExpHP](#): > > If you try to build this and are on linux with a reasonably-sized swap partition, you are very likely to send yourself into complete and utter turmoil. You’ve probably experienced this before doing something else similarly dumb: > > - The program eventually requires so much memory (and is using it so actively) that memory for other absolutely essential things (like your window manager) are paged out to swap, causing your system to stop responding. > - Soon, the program requires so much memory that not _even all of its own memory_ can fit in physical memory. The program’s execution is slowed down so much by constant page faults that it can’t even reach the point where it would OOM. I'd like to brag (let's be honest here :)) ; ok, I'm also hoping that someone finds this useful) that while I'm not using a swap (disabled support in kernel) and with the anti-freeze-OS-when-memory-pressure linux kernel patch (aka [le9d.patch](https://github.com/xftroxgpx/a3/blob/fa97258406c464627af36fa5eaafc65cb51976cf/system/Z575/OSes/3archlinux/on_baremetal/filesystem_now/archlinux/home/xftroxgpx/build/1packages/4used/kernel/linuxgit/le9d.patch#L1)) on 16G RAM, it takes 3mins 1sec for it to run(due to how slow `blowup` is eating memory) and then instantly get OOM-killed. I haven't tried WITH swap! but I can imagine some serious HDD thrashing(even with le9d.patch, or even [because](https://gist.github.com/constantoverride/84eba764f487049ed642eb2111a20830#gistcomment-2779445) of it! **WARNING** : do not use le9d.patch if you use swap!) ... > **** > > ```rust > /tmp/blo > $ time cargo run > !! LD_LIBRARY_PATH=/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib: > !! Executing '/home/xftroxgpx/build/2nonpkgs/rust.stuff/cargo/cargo//target/release//cargo' in pwd='/tmp/blo' with args: 'run' > Compiling blo v0.1.0 (/tmp/blo) > !! LD_LIBRARY_PATH=/tmp/blo/target/debug/deps:/home/xftroxgpx/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib:/home/xftroxgpx/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib: > !! Executing '/home/xftroxgpx/.cargo/bin/rustc' in pwd='/tmp/blo' with args: '--edition=2018 --crate-name blo /tmp/blo/src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=7ec1425a3afaa712 -C extra-filename=-7ec1425a3afaa712 --out-dir /tmp/blo/target/debug/deps -C incremental=/tmp/blo/target/debug/incremental -L dependency=/tmp/blo/target/debug/deps' > error: Could not compile `blo`. > > Caused by: > process didn't exit successfully: `rustc --edition=2018 --crate-name blo /tmp/blo/src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=7ec1425a3afaa712 -C extra-filename=-7ec1425a3afaa712 --out-dir /tmp/blo/target/debug/deps -C incremental=/tmp/blo/target/debug/incremental -L dependency=/tmp/blo/target/debug/deps` (signal: 9, SIGKILL: kill) > > real 3m1.251s > user 2m47.760s > sys 0m9.656s > > ``` > > dmesg: > > ```rust > [90226.015042] rustc invoked oom-killer: gfp_mask=0x6280ca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), order=0, oom_score_adj=0 > [90226.015049] CPU: 2 PID: 23149 Comm: rustc Kdump: loaded Tainted: G I 5.0.0-rc1-gbfeffd155283 #33 > [90226.015051] Hardware name: LENOVO Sabine/Torpedo, BIOS 54CN18WW 07/20/2011 > [90226.015052] Call Trace: > [90226.015059] dump_stack+0x46/0x60 > [90226.015063] dump_header+0x4f/0x369 > [90226.015065] ? sched_clock_local+0x12/0x90 > [90226.015068] oom_kill_process.cold.7+0xb/0x1e0 > [90226.015070] out_of_memory+0x195/0x560 > [90226.015072] __alloc_pages_nodemask+0xbbe/0xf00 > [90226.015076] alloc_pages_vma+0xa9/0x2a0 > [90226.015078] __handle_mm_fault+0xd7d/0x17b0 > [90226.015080] handle_mm_fault+0xee/0x270 > [90226.015083] __do_page_fault+0x188/0x430 > [90226.015086] ? page_fault+0x5/0x20 > [90226.015087] page_fault+0x1b/0x20 > [90226.015090] RIP: 0033:0x7f421868821b > [90226.015093] Code: 8d 34 39 49 89 75 60 48 8d 15 61 ca 13 00 49 39 d5 0f 95 c2 0f b6 d2 48 c1 e2 02 4c 09 fa 48 83 ca 01 48 89 51 08 48 83 c8 01 <48> 89 46 08 e9 ef fe ff ff 48 8b 72 28 48 8b 7e 08 48 89 fa 48 83 > [90226.015095] RSP: 002b:00007f421210b430 EFLAGS: 00010202 > [90226.015097] RAX: 0000000000000f01 RBX: fffffffffffffec0 RCX: 00007f3ea58b6ff0 > [90226.015098] RDX: 0000000000000115 RSI: 00007f3ea58b7100 RDI: 0000000000000004 > [90226.015099] RBP: 00007f421210b4f0 R08: 0000000000000003 R09: 00007f4204000080 > [90226.015100] R10: 00007f42040008d0 R11: 000000000000000f R12: 00007f4204000080 > [90226.015101] R13: 00007f4204000020 R14: 0000000000000000 R15: 0000000000000110 > [90226.015103] Mem-Info: > [90226.015108] active_anon:3417110 inactive_anon:32950 isolated_anon:0 > active_file:317214 inactive_file:9 isolated_file:0 > unevictable:8 dirty:212 writeback:0 unstable:0 > slab_reclaimable:77419 slab_unreclaimable:16944 > mapped:77330 shmem:33495 pagetables:12686 bounce:0 > free:34214 free_pcp:210 free_cma:0 > [90226.015112] Node 0 active_anon:13668440kB inactive_anon:131800kB active_file:1268856kB inactive_file:36kB unevictable:32kB isolated(anon):0kB isolated(file):0kB mapped:309320kB dirty:848kB writeback:0kB shmem:133980kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 925696kB writeback_tmp:0kB unstable:0kB all_unreclaimable? yes > [90226.015114] Node 0 DMA free:15900kB min:68kB low:84kB high:100kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15984kB managed:15900kB mlocked:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB > [90226.015118] lowmem_reserve[]: 0 2810 15303 15303 > [90226.015120] Node 0 DMA32 free:62176kB min:12396kB low:15492kB high:18588kB active_anon:2856340kB inactive_anon:40kB active_file:0kB inactive_file:88kB unevictable:0kB writepending:0kB present:3119616kB managed:2923008kB mlocked:0kB kernel_stack:16kB pagetables:2968kB bounce:0kB free_pcp:744kB local_pcp:488kB free_cma:0kB > [90226.015123] lowmem_reserve[]: 0 0 12492 12492 > [90226.015125] Node 0 Normal free:58780kB min:59212kB low:72988kB high:86764kB active_anon:10811848kB inactive_anon:131760kB active_file:1268800kB inactive_file:84kB unevictable:32kB writepending:848kB present:13090816kB managed:12797060kB mlocked:32kB kernel_stack:8784kB pagetables:47776kB bounce:0kB free_pcp:96kB local_pcp:44kB free_cma:0kB > [90226.015128] lowmem_reserve[]: 0 0 0 0 > [90226.015130] Node 0 DMA: 1*4kB (U) 1*8kB (U) 1*16kB (U) 0*32kB 2*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB (M) 3*4096kB (M) = 15900kB > [90226.015136] Node 0 DMA32: 167*4kB (U) 265*8kB (UM) 285*16kB (U) 245*32kB (U) 175*64kB (U) 98*128kB (U) 61*256kB (U) 13*512kB (U) 1*1024kB (U) 0*2048kB 0*4096kB = 62228kB > [90226.015142] Node 0 Normal: 2225*4kB (UME) 527*8kB (UE) 966*16kB (UME) 691*32kB (UME) 79*64kB (UME) 27*128kB (ME) 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 59196kB > [90226.015148] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=1048576kB > [90226.015150] Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB > [90226.015151] 350315 total pagecache pages > [90226.015152] 4056604 pages RAM > [90226.015152] 0 pages HighMem/MovableOnly > [90226.015153] 122612 pages reserved > [90226.015154] 0 pages cma reserved > [90226.015155] Tasks state (memory values in pages): > [90226.015155] [pid] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name > [90226.015160] [244] 0 244 385365 4023 3076096 0 0 systemd-journal > [90226.015163] [272] 0 272 9930 1813 102400 0 -1000 systemd-udevd > [90226.015165] [424] 81 424 2788 1072 65536 0 -900 dbus-daemon > [90226.015167] [427] 0 427 606 21 45056 0 0 gpm > [90226.015169] [430] 0 430 7361 1542 94208 0 0 systemd-logind > [90226.015171] [494] 0 494 12301 836 135168 0 0 login > [90226.015173] [622] 1000 622 8250 2095 102400 0 0 systemd > [90226.015175] [623] 1000 623 17413 501 163840 0 0 (sd-pam) > [90226.015177] [632] 1000 632 4545 3658 77824 0 0 bash > [90226.015179] [783] 1000 783 1807 881 49152 0 0 startx > [90226.015181] [805] 1000 805 1983 274 57344 0 0 xinit > [90226.015183] [806] 1000 806 102012 21360 462848 0 0 Xorg > [90226.015185] [811] 1000 811 141222 13898 421888 0 0 xfce4-session > [90226.015187] [815] 1000 815 2786 715 57344 0 0 dbus-daemon > [90226.015189] [819] 1000 819 77595 1584 102400 0 0 at-spi-bus-laun > [90226.015191] [825] 1000 825 2737 1041 53248 0 0 dbus-daemon > [90226.015192] [828] 1000 828 42521 1592 102400 0 0 at-spi2-registr > [90226.015194] [831] 1000 831 57836 1426 77824 0 0 xfconfd > [90226.015196] [838] 102 838 494820 5670 229376 0 0 polkitd > [90226.015198] [854] 1000 854 1453 119 45056 0 0 ssh-agent > [90226.015200] [859] 1000 859 39185 827 65536 0 0 gpg-agent > [90226.015202] [862] 1000 862 127425 18420 458752 0 0 xfwm4 > [90226.015203] [866] 1000 866 76923 8686 241664 0 0 xfce4-panel > [90226.015205] [869] 1000 869 74053 5454 212992 0 0 Thunar > [90226.015207] [871] 1000 871 76902 8493 245760 0 0 xfdesktop > [90226.015209] [873] 1000 873 119087 9506 266240 0 0 xfce4-terminal > [90226.015211] [874] 1000 874 120220 20772 368640 0 0 xfce4-terminal > [90226.015213] [885] 1000 885 53662 5038 188416 0 0 polkit-gnome-au > [90226.015215] [892] 1000 892 257244 3500 290816 0 0 pulseaudio > [90226.015216] [894] 1000 894 55847 6567 208896 0 0 xfce4-power-man > [90226.015218] [897] 133 897 38715 668 65536 0 0 rtkit-daemon > [90226.015220] [905] 1000 905 2671 841 61440 0 0 dbus-daemon > [90226.015222] [908] 1000 908 73800 6626 212992 0 0 xfce4-notifyd > [90226.015224] [914] 0 914 65190 2312 122880 0 0 upowerd > [90226.015226] [930] 1000 930 156584 11495 307200 0 0 panel-16-whiske > [90226.015228] [931] 1000 931 63049 1677 122880 0 0 gsettings-helpe > [90226.015230] [943] 1000 943 67215 7390 237568 0 0 panel-22-screen > [90226.015231] [948] 1000 948 55081 5966 196608 0 0 panel-12-system > [90226.015233] [952] 1000 952 52638 3720 176128 0 0 panel-24-cpugra > [90226.015235] [963] 1000 963 64016 5139 225280 0 0 xfsettingsd > [90226.015237] [971] 1000 971 84494 35561 442368 0 0 panel-20-cpufre > [90226.015239] [976] 0 976 11307 1492 122880 0 0 sudo > [90226.015241] [989] 1000 989 55080 5997 204800 0 0 panel-13-netloa > [90226.015242] [995] 1000 995 55070 5947 204800 0 0 panel-10-diskpe > [90226.015244] [1012] 1000 1012 55077 5934 208896 0 0 panel-4-diskper > [90226.015246] [1014] 1000 1014 55302 6188 204800 0 0 panel-8-xfce4-s > [90226.015248] [1022] 1000 1022 54817 5305 204800 0 0 panel-6-systray > [90226.015250] [1026] 1000 1026 52353 4234 180224 0 0 panel-25-xfce4- > [90226.015252] [1029] 1000 1029 55124 6121 204800 0 0 panel-2-actions > [90226.015253] [1061] 0 1061 1839 889 49152 0 0 cpuvary > [90226.015255] [1079] 0 1079 1839 751 49152 0 0 cpuvary > [90226.015257] [1011] 1000 1011 39342 1841 65536 0 0 dconf-service > [90226.015259] [32469] 1000 32469 4550 3712 81920 0 0 bash > [90226.015261] [6899] 1000 6899 1807 853 53248 0 0 v > [90226.015263] [6907] 1000 6907 4889 2624 81920 0 0 vim > [90226.015265] [10189] 1000 10189 4558 3751 86016 0 0 bash > [90226.015267] [10542] 0 10542 11307 1502 126976 0 0 sudo > [90226.015269] [10619] 0 10619 1841 943 53248 0 0 freepagecachepa > [90226.015270] [19277] 1000 19277 4555 3670 81920 0 0 bash > [90226.015272] [19492] 1000 19492 1809 851 49152 0 0 v > [90226.015274] [19500] 1000 19500 4891 2623 81920 0 0 vim > [90226.015276] [12198] 1000 12198 1843 964 53248 0 0 ccachewatch > [90226.015278] [29108] 1000 29108 4556 3700 81920 0 0 bash > [90226.015280] [29695] 1000 29695 1842 981 49152 0 0 earl > [90226.015282] [29703] 1000 29703 471717 29831 700416 0 0 vlc > [90226.015284] [16882] 1000 16882 4556 3690 77824 0 0 bash > [90226.015286] [17034] 1000 17034 1842 959 49152 0 0 chro2 > [90226.015288] [17079] 1000 17079 1842 963 53248 0 0 chro > [90226.015290] [17085] 1000 17085 1336 191 53248 0 0 tail > [90226.015292] [17086] 1000 17086 2468 557 57344 0 0 sed > [90226.015294] [17087] 1000 17087 2468 557 61440 0 0 sed > [90226.015296] [17092] 1000 17092 214921 46419 909312 0 0 chromium > [90226.015298] [17137] 1000 17137 52121 8375 327680 0 0 chromium > [90226.015300] [17168] 1000 17168 52121 1950 229376 0 0 chromium > [90226.015302] [17302] 1000 17302 172144 23140 1085440 0 300 chromium > [90226.015304] [17391] 1000 17391 165225 17645 1216512 0 300 chromium > [90226.015306] [17419] 1000 17419 178886 25315 1507328 0 300 chromium > [90226.015308] [17823] 1000 17823 212661 39830 2691072 0 300 chromium > [90226.015310] [17937] 1000 17937 184832 20550 1208320 0 300 chromium > [90226.015312] [18106] 1000 18106 185088 21443 1261568 0 300 chromium > [90226.015313] [18123] 1000 18123 163993 21905 1196032 0 300 chromium > [90226.015315] [22945] 1000 22945 205783 45995 2412544 0 300 chromium > [90226.015317] [25232] 1000 25232 190036 28565 1519616 0 300 chromium > [90226.015319] [30814] 1000 30814 196907 34834 1822720 0 300 chromium > [90226.015321] [3535] 1000 3535 173888 19992 1081344 0 300 chromium > [90226.015323] [6365] 1000 6365 190421 29221 1507328 0 300 chromium > [90226.015325] [14817] 1000 14817 162486 15613 847872 0 300 chromium > [90226.015327] [21025] 1000 21025 181996 23917 1544192 0 300 chromium > [90226.015329] [9318] 1000 9318 196007 33045 1683456 0 300 chromium > [90226.015331] [21166] 1000 21166 4589 3782 86016 0 0 bash > [90226.015333] [22693] 1000 22693 4556 3722 81920 0 0 bash > [90226.015335] [22783] 1000 22783 3403 952 69632 0 0 top > [90226.015337] [23133] 1000 23133 43107 3760 118784 0 0 cargo > [90226.015339] [23142] 1000 23142 3519630 3070599 24883200 0 0 rustc > [90226.015341] [24817] 1000 24817 4736 3887 77824 0 0 bash > [90226.015343] [25014] 1000 25014 1503 686 49152 0 0 watch > [90226.015345] [29721] 1000 29721 1328 176 49152 0 0 sleep > [90226.015347] [31821] 1000 31821 4556 3672 77824 0 0 bash > [90226.015349] [31951] 1000 31951 1528 676 49152 0 0 dmesg > [90226.015351] [2223] 0 2223 1325 191 49152 0 0 sleep > [90226.015353] [2493] 0 2493 1325 174 49152 0 0 sleep > [90226.015354] oom-kill:constraint=CONSTRAINT_NONE,nodemask=(null),cpuset=/,mems_allowed=0,global_oom,task_memcg=/user.slice/user-1000.slice/session-c1.scope,task=rustc,pid=23142,uid=1000 > [90226.015362] Out of memory: Kill process 23142 (rustc) score 782 or sacrifice child > [90226.015375] Killed process 23142 (rustc) total-vm:14078520kB, anon-rss:12236960kB, file-rss:45436kB, shmem-rss:0kB > [90226.404344] oom_reaper: reaped process 23142 (rustc), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB > > ``` ---
**Author:** ![system](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/system/32/14092_2.png) [@system](https://internals.rust-lang.org/u/system)\ **Post date:** [April 17, 2019, 10:44am UTC](https://internals.rust-lang.org/t/thought-saving-users-from-themselves-in-macros-that-explode/7907/8 "2019-04-17T10:44:10Z")
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