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[API] Fix -Werror=alloc-size-larger-than= warning in runtime_context.h #3709

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Merged
marcalff merged 2 commits into from
Oct 23, 2025
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[API] Fix -Werror=alloc-size-larger-than= warning in runtime_context.h #3709

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[API] Fix -Werror=alloc-size-larger-than= warning in runtime_context.h
marcalff Oct 22, 2025
5f23f20
Merge branch 'main' into fix_runtime_context_warning
marcalff Oct 22, 2025
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39 changes: 39 additions & 0 deletions api/include/opentelemetry/context/runtime_context.h
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Original file line number Diff line number Diff line change
Expand Up @@ -241,6 +241,26 @@ class ThreadLocalContextStorage : public RuntimeContextStorage
{
friend class ThreadLocalContextStorage;

/**
* Limit the max stack depth.
* The stack will still work beyond this limit,
* counting push() and pop() properly,
* but will not record contexts.
*
* In practice, this should not affect instrumented applications,
* the limit is set to 1 million nested scopes.
*
* The whole reason for this limit to exist is to prevent
* compiler warnings like:
* error: argument 1 value ‘18446744073709551615’
* exceeds maximum object size 9223372036854775807
* [-Werror=alloc-size-larger-than=]
* on this line of code:
* Context *temp = new Context[new_capacity];
* when compiling with gcc and optimizations (-flto).
*/
static constexpr size_t max_capacity_ = 1000000;

Stack() noexcept : size_(0), capacity_(0), base_(nullptr) {}

// Pops the top Context off the stack.
Expand All @@ -250,6 +270,11 @@ class ThreadLocalContextStorage : public RuntimeContextStorage
{
return;
}
if (size_ > max_capacity_)
{
size_ -= 1;
return;
}
// Store empty Context before decrementing `size`, to ensure
// the shared_ptr object (if stored in prev context object ) are released.
// The stack is not resized, and the unused memory would be reutilised
Expand Down Expand Up @@ -278,6 +303,10 @@ class ThreadLocalContextStorage : public RuntimeContextStorage
{
return Context();
}
if (size_ > max_capacity_)
{
return Context();
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@lalitb lalitb Oct 23, 2025

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Just curious - should it return the last valid context, instead of empty one ?

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@marcalff marcalff Oct 23, 2025

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Good question.

In my understanding, Scope will attach and detach contexts on creation and destruction, adding/removing from the stack.

If the code returns the last valid context, then we will have:

  • every scope nested at depth max_capacity_, max_capacity_ + 1, ..., max_capacity_ + N share the same context.
  • Scope at max_capacity_ + N will destroy the last valid scope on destruction, causing side effects.

So, I think Top() and Pop() should return an empty context instead, once the stack depth goes beyond the limit.

This is very theoretical, because any process with 1 million nested scopes in the call stack will never reach this point, being long dead, already killed for other reasons (stack overflow, out of memory).

}
return base_[size_ - 1];
}

Expand All @@ -286,6 +315,10 @@ class ThreadLocalContextStorage : public RuntimeContextStorage
void Push(const Context &context) noexcept
{
size_++;
if (size_ > max_capacity_)
{
return;
}
if (size_ > capacity_)
{
Resize(size_ * 2);
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@Reneg973 Reneg973 Oct 25, 2025 •
edited
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@marcalff
Did you see this line?
Resize(size_ * 2);

Expand All @@ -299,8 +332,14 @@ class ThreadLocalContextStorage : public RuntimeContextStorage
size_t old_size = size_ - 1;
if (new_capacity == 0)
{
// First increase
new_capacity = 2;
}
if (new_capacity > max_capacity_)
{
// Last increase
new_capacity = max_capacity_;
}
Context *temp = new Context[new_capacity];
if (base_ != nullptr)
{
Expand Down
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