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| author | Russ Cox <rsc@golang.org> | 2014-05-28 19:50:19 -0400 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2014-05-28 19:50:19 -0400 |
| commit | 73044738e146bec259f7b8e89ecc816a421921aa (patch) | |
| tree | 181e98d4a3bba678b89ab4f80452cf58daaeed13 /src/cmd/8g | |
| parent | 76fe11c57b2efe4c1ffb53730efadcd928e976c2 (diff) | |
| download | go-73044738e146bec259f7b8e89ecc816a421921aa.tar.gz | |
cmd/gc: fix x=x crash
The 'nodarg' function is used to obtain a Node*
representing a function argument or result.
It returned a brand new Node*, but that violates
the guarantee in most places in the compiler that
two Node*s refer to the same variable if and only if
they are the same Node* pointer. Reestablish that
invariant by making nodarg return a preexisting
named variable if present.
Having fixed that, avoid any copy during x=x in
componentgen, because the VARDEF we emit
before the copy marks the lhs x as dead incorrectly.
The change in walk.c avoids modifying the result
of nodarg. This was the only place in the compiler
that did so.
Fixes issue 8097.
LGTM=r, khr
R=golang-codereviews, r, khr
CC=golang-codereviews, iant
https://codereview.appspot.com/102820043
Diffstat (limited to 'src/cmd/8g')
| -rw-r--r-- | src/cmd/8g/cgen.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/src/cmd/8g/cgen.c b/src/cmd/8g/cgen.c index 1aae7771c..d626c2eb0 100644 --- a/src/cmd/8g/cgen.c +++ b/src/cmd/8g/cgen.c @@ -1397,6 +1397,13 @@ componentgen(Node *nr, Node *nl) } } + // nl and nr are 'cadable' which basically means they are names (variables) now. + // If they are the same variable, don't generate any code, because the + // VARDEF we generate will mark the old value as dead incorrectly. + // (And also the assignments are useless.) + if(nr != N && nl->op == ONAME && nr->op == ONAME && nl == nr) + goto yes; + switch(nl->type->etype) { case TARRAY: if(nl->op == ONAME) |