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AVRO-4185: [C++] Use a temp file in StreamTests #3496

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AVRO-4185: [C++] Use a temp file in StreamTests #3496

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AVRO-4185: [C++] Use a temp file in StreamTests
gahr Sep 22, 2025
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Update lang/c++/test/StreamTests.cc
gahr Oct 23, 2025
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23 changes: 11 additions & 12 deletions lang/c++/test/StreamTests.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include <boost/test/included/unit_test.hpp>
#include <boost/test/parameterized_test.hpp>

#include <cstdio>
#include <filesystem>

namespace avro {
Expand Down Expand Up @@ -134,36 +135,34 @@ void testNonEmpty2(const TestData &td) {
Verify1()(*is, td.dataSize);
}

static const char filename[] = "test_str.bin";

struct FileRemover {
const std::filesystem::path file;
explicit FileRemover(const char *fn) : file(fn) {}
~FileRemover() { std::filesystem::remove(file); }
struct FileGuard {
const std::filesystem::path path{ std::tmpnam(nullptr) };
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Using std::tmpnam(nullptr) is unsafe as it can cause race conditions and security vulnerabilities. Consider using std::filesystem::temp_directory_path() with a unique filename generator or platform-specific secure temporary file functions instead.

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@gahr gahr Sep 22, 2025 •
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I don't think these concerns apply to this test code.

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@martin-g martin-g Oct 23, 2025

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Isn't tmpnam deprecated ?

Avro uses C++17, so we can use something like the following instead:

#include <random>
...
std::filesystem::path path = std::filesystem::temp_directory_path() / 
    ("avro_test_" + std::to_string(std::random_device{}()));

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@gahr gahr Oct 23, 2025

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Isn't tmpnam deprecated ?

I can't find references to its deprecation.

I don't think using std::random_device is a good idea, as it can be implemented using a PRNG, i.e., two tests running at the same time would produce the same number.

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@martin-g martin-g Oct 23, 2025

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https://learn.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2010/hs3e7355(v=vs.100)
In the example code there is // Note: tmpnam is deprecated; consider using tmpnam_s instead

Also in the build logs we can see:

2025-10-23T08:00:00.3420284Z [ 68%] Linking CXX executable StreamTests
2025-10-23T08:00:00.4955456Z /usr/bin/ld: CMakeFiles/StreamTests.dir/test/StreamTests.cc.o: in function `avro::stream::FileGuard::FileGuard()':
2025-10-23T08:00:00.4957287Z /home/runner/work/avro/avro/lang/c++/test/StreamTests.cc:138:(.text._ZN4avro6stream9FileGuardC2Ev[_ZN4avro6stream9FileGuardC5Ev]+0x2a): warning: the use of `tmpnam' is dangerous, better use `mkstemp'
2025-10-23T08:00:00.6147334Z [ 68%] Built target StreamTests

https://productionresultssa3.blob.core.windows.net/actions-results/abfc1b86-599c-48bd-a249-acda8f187020/workflow-job-run-670f0204-095a-5c23-a7d3-1d13fabc5e69/logs/job/job-logs.txt?rsct=text%2Fplain&se=2025-10-23T08%3A12%3A13Z&sig=9G%2FOy2gomdBnbYY%2FXTGGg%2Fza%2BjuKKXvqJVAL4xpemfg%3D&ske=2025-10-23T17%3A45%3A39Z&skoid=ca7593d4-ee42-46cd-af88-8b886a2f84eb&sks=b&skt=2025-10-23T05%3A45%3A39Z&sktid=398a6654-997b-47e9-b12b-9515b896b4de&skv=2025-11-05&sp=r&spr=https&sr=b&st=2025-10-23T08%3A02%3A08Z&sv=2025-11-05

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@gahr gahr Oct 23, 2025

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I don't have a more standard way, sorry.

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@thiru-mg thiru-mg Dec 5, 2025

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Since random_device() is meant to be used for seeding a PNRG and not directly for generating random numbers, we can do something like:

static std::random_device rdev;
static std::mt19937 rng(rdev());

struct FileGuard {
    const std::filesystem::path path{ rng() };
    ...
 }

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@gahr gahr Dec 5, 2025

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This doesn't address my concern: two processes can still generate the same sequence.

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@thiru-mg thiru-mg Dec 5, 2025 •
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Remember the code is in test. The conflict happens when two people run the run the exactly at the same sub-microsecond. How likely is it? Even if happens, who cares? Just rerun the test. It is anyway better than what we have now.
If we are still paranoid, let's xor the value of random_device() with pid.

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@gahr gahr Dec 5, 2025

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Where is the spec that say that random_device must be implemented in such a way? In the standard I read it can generate the same sequence each time.

~FileGuard() { std::filesystem::remove(path); }
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@martin-g martin-g Oct 23, 2025

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Should we care about failures in remove() here ?
Or since it is a test we don't care ?

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@gahr gahr Oct 23, 2025

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I would not care, and I wouldn't know how to recover from such an error.

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@martin-g martin-g Oct 23, 2025

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Not recover, but log it.
But this is minor. We can ignore it.

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@thiru-mg thiru-mg Oct 23, 2025

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If we fail to remove(), it is not catastrophic, but it would point to a bug somewhere. At lease we should report the error.

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@gahr gahr Oct 23, 2025

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A bug, or some temporary condition.

const char* filename() const { return path.c_str(); }
};

template<typename V>
void testEmpty_fileStream() {
FileRemover fr(filename);
FileGuard fg;
{
std::unique_ptr<OutputStream> os = fileOutputStream(filename);
std::unique_ptr<OutputStream> os = fileOutputStream(fg.filename());
}
std::unique_ptr<InputStream> is = fileInputStream(filename);
std::unique_ptr<InputStream> is = fileInputStream(fg.filename());
V()
(*is);
}

template<typename F, typename V>
void testNonEmpty_fileStream(const TestData &td) {
FileRemover fr(filename);
FileGuard fg;
{
std::unique_ptr<OutputStream> os = fileOutputStream(filename,
std::unique_ptr<OutputStream> os = fileOutputStream(fg.filename(),
td.chunkSize);
F()
(*os, td.dataSize);
}

std::unique_ptr<InputStream> is = fileInputStream(filename, td.chunkSize);
std::unique_ptr<InputStream> is = fileInputStream(fg.filename(), td.chunkSize);
V()
(*is, td.dataSize);
}
Expand Down