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compiler: avoid undefined behavior in Import::read

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For some implementations of Stream, advancing the stream will invalidate
the previously-returned peek buffer. Copy the peek buffer before
advancing in Import::read to avoid this undefined behavior.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/259438
This commit is contained in:
Nikhil Benesch 2020-10-04 23:40:40 -04:00 committed by Ian Lance Taylor
parent fcae512115
commit f5431aeaf5
4 changed files with 11 additions and 10 deletions
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2
gcc/go/gofrontend/MERGE
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@ -1,4 +1,4 @@
d00febdab0535546ccbf1ef634be1f23b09c8b77
613e530547549f4220c4571ea913acbe5fa56f72
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.

2
gcc/go/gofrontend/gogo.cc
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@ -6212,7 +6212,7 @@ Function::import_func(Import* imp, std::string* pname,
return false;
}
*body = imp->read(static_cast<size_t>(llen));
imp->read(static_cast<size_t>(llen), body);
}
return true;

9
gcc/go/gofrontend/import.cc
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@ -1375,8 +1375,8 @@ Import::read_name()
// Read LENGTH bytes from the stream.
std::string
Import::read(size_t length)
void
Import::read(size_t length, std::string* out)
{
const char* data;
if (!this->stream_->peek(length, &data))
@ -1385,10 +1385,11 @@ Import::read(size_t length)
go_error_at(this->location_, "import error at %d: expected %d bytes",
this->stream_->pos(), static_cast<int>(length));
this->stream_->set_saw_error();
return "";
*out = std::string("");
return;
}
*out = std::string(data, length);
this->advance(length);
return std::string(data, length);
}
// Turn a string into a integer with appropriate error handling.

8
gcc/go/gofrontend/import.h
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@ -240,10 +240,10 @@ class Import : public Import_expression
get_char()
{ return this->stream_->get_char(); }
// Read LENGTH characters into a string and advance past them. On
// EOF reports an error and returns an empty string.
std::string
read(size_t length);
// Read LENGTH characters into *OUT and advance past them. On
// EOF reports an error and sets *OUT to an empty string.
void
read(size_t length, std::string* out);
// Return true at the end of the stream.
bool