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Go CFG: anchor result-read epilogue on Normal Exit via new hooks

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This commit is contained in:
Owen Mansel-Chan
2026-06-16 14:49:23 +01:00
parent 28afda1726
commit f5eef7d3d7
1 changed files with 26 additions and 10 deletions
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36
go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll
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@@ -740,6 +740,25 @@ module GoCfg {
)
}
predicate overridesCallableEndAbruptCompletion(Ast::Callable c, AbruptCompletion completion) {
// For functions with result variables, the library's default routing of a
// `return` straight to the normal exit node is suppressed so that the
// return is instead caught by `endAbruptCompletion` above and routed
// through the result-read epilogue.
exists(c.(Go::FuncDef).getResultVar(0)) and
completion.getSuccessorType() instanceof ReturnSuccessor
}
predicate callableExitStep(PreControlFlowNode n, Ast::Callable c, boolean normal) {
// The last result-read node of the epilogue steps to the normal exit node.
exists(Go::FuncDef fd, int j | fd = c |
normal = true and
exists(fd.getResultVar(j)) and
not exists(fd.getResultVar(j + 1)) and
n.isAdditional(fd.getBody(), "result-read:" + j.toString())
)
}
predicate step(PreControlFlowNode n1, PreControlFlowNode n2) {
rangeLoop(n1, n2) or
switchStmt(n1, n2) or
@@ -1566,9 +1585,10 @@ module GoCfg {
* - Prologue: Before(body) → arg:-1 → param-init:-1 → arg:0 → param-init:0 → ...
* when a receiver exists; otherwise it starts at arg:0. Then
* result-zero-init:0 → result-init:0 → ... → first statement
* - Epilogue: return → result-read:0 → result-read:1 → ... → After(body)
* - Epilogue: return → result-read:0 → result-read:1 → ... → result-read:last
*
* `After(body)` goes to `NormalExit(fd)` via the shared library's built-in step.
* The last result-read node goes to `NormalExit(fd)` via the shared
* library's `callableExitStep` hook.
*/
private predicate hasFuncDefPrologue(Go::FuncDef fd) {
exists(fd.getParameter(_)) or exists(fd.getResultVar(_))
@@ -1667,15 +1687,11 @@ module GoCfg {
or
funcDefBodyStep(fd, n1, n2)
or
// result-read:j → result-read:(j+1) or After(body)
exists(int j | exists(fd.getResultVar(j)) |
// result-read:j → result-read:(j+1); the last result-read node steps to
// the normal exit node via the `callableExitStep` hook.
exists(int j | exists(fd.getResultVar(j + 1)) |
n1.isAdditional(fd.getBody(), "result-read:" + j.toString()) and
(
exists(fd.getResultVar(j + 1)) and
n2.isAdditional(fd.getBody(), "result-read:" + (j + 1).toString())
or
not exists(fd.getResultVar(j + 1)) and n2.isAfter(fd.getBody())
)
n2.isAdditional(fd.getBody(), "result-read:" + (j + 1).toString())
)
)
}