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C++: Enforce uniqueness in the other branch of 'getSize'.

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Mathias Vorreiter Pedersen
2026-01-26 15:00:58 +00:00
parent 91752e5307
commit 13a5249a9d
1 changed files with 26 additions and 24 deletions
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50
cpp/ql/lib/semmle/code/cpp/commons/Buffer.qll
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@@ -81,30 +81,32 @@ private int getSize(VariableAccess va) {
not v instanceof Field and
result = getVariableSize(v)
or
exists(Class c, int trueSize |
// Otherwise, we find the "outermost" object and compute the size
// as the difference between the size of the type of the "outermost
// object" and the offset of the field relative to that type.
// For example, consider the following structs:
// ```
// struct S {
// uint32_t x;
// uint32_t y;
// };
// struct S2 {
// S s;
// uint32_t z;
// };
// ```
// Given an object `S2 s2` the size of the buffer `&s2.s.y`
// is the size of the base object type (i.e., `S2`) minutes the offset
// of `y` relative to the type `S2` (i.e., `4`). So the size of the
// buffer is `12 - 4 = 8`.
c = getRootType(va) and
// we calculate the size based on the last field, to avoid including any padding after it
trueSize = max(Field f | | f.getOffsetInClass(c) + getVariableSize(f)) and
result = trueSize - v.(Field).getOffsetInClass(c)
)
result =
unique(Class c, int trueSize |
// Otherwise, we find the "outermost" object and compute the size
// as the difference between the size of the type of the "outermost
// object" and the offset of the field relative to that type.
// For example, consider the following structs:
// ```
// struct S {
// uint32_t x;
// uint32_t y;
// };
// struct S2 {
// S s;
// uint32_t z;
// };
// ```
// Given an object `S2 s2` the size of the buffer `&s2.s.y`
// is the size of the base object type (i.e., `S2`) minutes the offset
// of `y` relative to the type `S2` (i.e., `4`). So the size of the
// buffer is `12 - 4 = 8`.
c = getRootType(va) and
// we calculate the size based on the last field, to avoid including any padding after it
trueSize = max(Field f | | f.getOffsetInClass(c) + getVariableSize(f))
|
trueSize - v.(Field).getOffsetInClass(c)
)
)
}