Hello,
While upgrading compilers from GCC 4.7 to GCC 7.2 on an embedded device, I
noticed a substantial increase in memory usage while parsing a file upload
request.
This seems to be caused by changed behavior in std::string. As GCC 4.7 was
using copy-on-write and refcounting for std::string, a string copy did not
cause a copy of the data. Now with GCC 7.2, a string copy also copies the data.
For some large (+30MB) requests, this now makes our application go
out-of-memory on a embedded device with only 128MB of RAM.
To bring memory usage back to the GCC 4.7 values, I patched Cgicc::parseMIME to
std::move the data to the FormFile and FormEntry (see attached patch).
As this patch is using some C++ 11 features, I was wondering if you do accept
patches that (conditionally) use C++ 11 (or higher) features?
I could rework the patch to only use those features when supported by the
__cplusplus version.
Best Regards,
Dries
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diff -urN cgicc.orig/Cgicc.cpp cgicc/Cgicc.cpp
--- cgicc.orig/Cgicc.cpp 2017-06-27 21:38:02.000000000 +0200
+++ cgicc/Cgicc.cpp 2018-03-26 08:30:13.507547000 +0200
@@ -497,10 +497,10 @@
MultipartHeader head = parseHeader(data.substr(0, valueStart));
if(head.getFilename().empty())
- fFormData.push_back(FormEntry(head.getName(), value));
+ fFormData.emplace_back(head.getName(), std::move(value));
else
- fFormFiles.push_back(FormFile(head.getName(),
+ fFormFiles.emplace_back(head.getName(),
head.getFilename(),
head.getContentType(),
- value));
+ std::move(value));
}
diff -urN cgicc.orig/FormEntry.h cgicc/FormEntry.h
--- cgicc.orig/FormEntry.h 2017-06-27 21:38:02.000000000 +0200
+++ cgicc/FormEntry.h 2018-03-26 08:29:15.767638000 +0200
@@ -97,6 +97,11 @@
const std::string& value)
: fName(name), fValue(value)
{}
+ inline
+ FormEntry(std::string&& name,
+ std::string&& value)
+ : fName(std::forward<std::string>(name)), fValue(std::forward<std::string>(value))
+ {}
/*!
* \brief Copy constructor.
diff -urN cgicc.orig/FormFile.cpp cgicc/FormFile.cpp
--- cgicc.orig/FormFile.cpp 2017-06-27 21:38:02.000000000 +0200
+++ cgicc/FormFile.cpp 2018-03-26 09:14:43.750957309 +0200
@@ -39,6 +39,17 @@
fDataType = dataType.empty() ? std::string("text/plain") : dataType;
}
+cgicc::FormFile::FormFile(std::string&& name,
+ std::string&& filename,
+ std::string&& dataType,
+ std::string&& data)
+ : fName(std::forward<std::string>(name)),
+ fFilename(std::forward<std::string>(filename)),
+ fData(std::forward<std::string>(data))
+{
+ fDataType = dataType.empty() ? std::string("text/plain") : dataType;
+}
+
bool
cgicc::FormFile::operator== (const FormFile& file) const
{
diff -urN cgicc.orig/FormFile.h cgicc/FormFile.h
--- cgicc.orig/FormFile.h 2017-06-27 21:38:02.000000000 +0200
+++ cgicc/FormFile.h 2018-03-26 08:59:01.813701000 +0200
@@ -92,6 +92,10 @@
const std::string& filename,
const std::string& dataType,
const std::string& data);
+ FormFile(std::string&& name,
+ std::string&& filename,
+ std::string&& dataType,
+ std::string&& data);
/*!
* \brief Copy constructor.
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