diff options
| -rw-r--r-- | lib/system.nim | 9 | ||||
| -rw-r--r-- | lib/system/strs_v2.nim | 2 |
2 files changed, 9 insertions, 2 deletions
diff --git a/lib/system.nim b/lib/system.nim index 56746fb65..605670f44 100644 --- a/lib/system.nim +++ b/lib/system.nim @@ -3124,5 +3124,12 @@ when not defined(createNimHcr) and not defined(nimscript): when notJSnotNims and not defined(nimSeqsV2): proc prepareStrMutation*(s: var string) {.inline.} = ## String literals (e.g. "abc", etc) in the ARC/ORC mode are "copy on write", - ## therefore you should call `prepareStrMutation` before modifying the strings. + ## therefore you should call `prepareStrMutation` before modifying the strings + ## via `addr`. + runnableExamples("--gc:arc"): + var x = "abc" + var y = "defgh" + prepareStrMutation(y) # without this, you may get a `SIGBUS` or `SIGSEGV` + moveMem(addr y[0], addr x[0], x.len) + assert y == "abcgh" discard diff --git a/lib/system/strs_v2.nim b/lib/system/strs_v2.nim index b20457d51..2647f7dcc 100644 --- a/lib/system/strs_v2.nim +++ b/lib/system/strs_v2.nim @@ -171,7 +171,7 @@ proc nimPrepareStrMutationV2(s: var NimStringV2) {.compilerRtl, inline.} = proc prepareStrMutation*(s: var string) {.inline.} = # string literals are "copy on write", so you need to call - # `prepareStrMutation` before modifying the strings. + # `prepareStrMutation` before modifying the strings via `addr`. {.cast(noSideEffect).}: let s = unsafeAddr s nimPrepareStrMutationV2(cast[ptr NimStringV2](s)[]) |