Tag Archives: clang
Porting a PostgreSQL Extension from Unix to Windows 10
2ndQuadrant has written before about how to build your own extension for Windows. This time we take a look at what it takes to port one written by someone else. I am building this for PostgreSQL 11 on Windows using Visual Studio 2019 and clang.
Here we are working with the hashtypes extension. Unfortunately, at the time of writing, version 0.1.5 has not been released with the support for PostgreSQL 11. So we build one from git.
git clone https://github.com/adjust/hashtypes.git
The first thing we do is to take a look at the C source files. There are only four of them,
sha.c so we can be reasonably sure the porting effort will be quick.
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The Case of the Apparent NSS Memory Corruption
This is a story of my encounter with an apparent memory corruption issue in the Netscape Security Services library.
The source I’m discussing can be found on Github.
Usually, when I try to get acquainted with a new API, I start to write simple program, one API call by call, which I compile and run after each step.
Imagine my surprise, when after adding the following function call (the only thing I added)
PK11_FindKeyByAnyCert( certificate, passwd );
I got this memory corruption error.
dblfree(56630,0x7fff73f61300) malloc: *** error for object 0x7fd39250ce70: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug zsh: abort ./dblfree
The above error is taken from my minimal example of the problem, not the actual program I was working on at the time. The only difference is the name of the binary and the hex numbers.
So what is happening here? I didn’t know. And to find out, it’s really important to use the right tool for the job.
So the first thing I did was to instrument my code with the built-in OS X tools, instruments(1). That didn’t tell me much; either because it doesn’t help in this particular instance, or that I just don’t know how to use it.
I will make a note that some people suggested Valgrind. I didn’t go that way because the problem seems to be adequately described with the Clang Address Sanitizer.
Continue reading The Case of the Apparent NSS Memory Corruption