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Merge pull request #19511 from MathiasVP/as-expr-array-aggregate-literal
C++: Make `node.asExpr() instanceof ArrayAggregateLiteral` satisfiable
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‎cpp/ql/lib/change-notes/2025-05-16-array-aggregate-literals.md

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---
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category: fix
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---
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* Fixed a problem where `asExpr()` on `DataFlow::Node` would never return `ArrayAggregateLiteral`s.

‎cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/ExprNodes.qll

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@@ -45,6 +45,28 @@ private module Cached {
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)
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}
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private Expr getRankedElementExpr(ArrayAggregateLiteral aggr, int rnk) {
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result =
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rank[rnk + 1](Expr e, int elementIndex, int position |
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e = aggr.getElementExpr(elementIndex, position)
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|
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e order by elementIndex, position
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)
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}
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private class LastArrayAggregateStore extends StoreInstruction {
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ArrayAggregateLiteral aggr;
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LastArrayAggregateStore() {
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exists(int rnk |
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this.getSourceValue().getUnconvertedResultExpression() = getRankedElementExpr(aggr, rnk) and
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not exists(getRankedElementExpr(aggr, rnk + 1))
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)
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}
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ArrayAggregateLiteral getArrayAggregateLiteral() { result = aggr }
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}
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private Expr getConvertedResultExpressionImpl0(Instruction instr) {
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// IR construction inserts an additional cast to a `size_t` on the extent
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// of a `new[]` expression. The resulting `ConvertInstruction` doesn't have
@@ -95,6 +117,16 @@ private module Cached {
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tco.producesExprResult() and
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result = asDefinitionImpl0(instr)
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)
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or
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// IR construction breaks an array aggregate literal `{1, 2, 3}` into a
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// sequence of `StoreInstruction`s. So there's no instruction `i` for which
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// `i.getUnconvertedResultExpression() instanceof ArrayAggregateLiteral`.
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// So we map the instruction node corresponding to the last `Store`
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// instruction of the sequence to the result of the array aggregate
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// literal. This makes sense since this store will immediately flow into
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// the indirect node representing the array. So this node does represent
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// the array after it has been fully initialized.
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result = instr.(LastArrayAggregateStore).getArrayAggregateLiteral()
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}
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private Expr getConvertedResultExpressionImpl(Instruction instr) {

‎cpp/ql/test/library-tests/dataflow/asExpr/test.cpp

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@@ -35,6 +35,6 @@ void test_aggregate_literal() {
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S s5 = {.a = 1, .b = 2}; // $ asExpr=1 asExpr=2 asExpr={...}
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int xs[] = {1, 2, 3}; // $ asExpr=1 asExpr=2 asExpr=3 MISSING: asExpr={...}
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const int ys[] = {[0] = 4, [1] = 5, [0] = 6}; // $ asExpr=4 asExpr=5 asExpr=6 MISSING: asExpr={...}
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int xs[] = {1, 2, 3}; // $ asExpr=1 asExpr=2 asExpr=3 asExpr={...}
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const int ys[] = {[0] = 4, [1] = 5, [0] = 6}; // $ asExpr=4 asExpr=5 asExpr=6 asExpr={...}
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}

‎cpp/ql/test/query-tests/Security/CWE/CWE-134/semmle/consts/NonConstantFormat.expected

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| consts.cpp:24:7:24:9 | **gv1 | consts.cpp:25:2:25:4 | *a | provenance | |
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| consts.cpp:24:7:24:9 | **gv1 | consts.cpp:30:9:30:14 | *access to array | provenance | |
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| consts.cpp:24:7:24:9 | **gv1 | consts.cpp:123:2:123:12 | *... = ... | provenance | |
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| consts.cpp:25:2:25:4 | *a | consts.cpp:26:2:26:4 | *b | provenance | |
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| consts.cpp:26:2:26:4 | *b | consts.cpp:24:7:24:9 | **gv1 | provenance | |
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| consts.cpp:25:2:25:4 | *a | consts.cpp:26:2:26:4 | *{...} | provenance | |
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| consts.cpp:26:2:26:4 | *{...} | consts.cpp:24:7:24:9 | **gv1 | provenance | |
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| consts.cpp:29:7:29:25 | **nonConstFuncToArray | consts.cpp:126:9:126:30 | *call to nonConstFuncToArray | provenance | |
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| consts.cpp:30:9:30:14 | *access to array | consts.cpp:29:7:29:25 | **nonConstFuncToArray | provenance | |
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| consts.cpp:85:7:85:8 | gets output argument | consts.cpp:86:9:86:10 | *v1 | provenance | |
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| consts.cpp:85:7:85:8 | gets output argument | consts.cpp:129:19:129:20 | *v1 | provenance | |
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| consts.cpp:85:7:85:8 | gets output argument | consts.cpp:135:9:135:11 | *v10 | provenance | TaintFunction |
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| consts.cpp:90:2:90:14 | *... = ... | consts.cpp:91:9:91:10 | *v2 | provenance | |
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| consts.cpp:90:2:90:14 | *... = ... | consts.cpp:115:21:115:22 | *v2 | provenance | |
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| consts.cpp:90:2:90:14 | *... = ... | consts.cpp:115:21:115:22 | *{...} | provenance | |
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| consts.cpp:90:7:90:10 | *call to gets | consts.cpp:90:2:90:14 | *... = ... | provenance | |
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| consts.cpp:90:12:90:13 | gets output argument | consts.cpp:94:13:94:14 | *v1 | provenance | |
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| consts.cpp:90:12:90:13 | gets output argument | consts.cpp:99:2:99:8 | *... = ... | provenance | |
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| consts.cpp:106:13:106:19 | *call to varFunc | consts.cpp:107:9:107:10 | *v5 | provenance | |
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| consts.cpp:111:2:111:15 | *... = ... | consts.cpp:112:9:112:10 | *v6 | provenance | |
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| consts.cpp:111:7:111:13 | *call to varFunc | consts.cpp:111:2:111:15 | *... = ... | provenance | |
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| consts.cpp:115:17:115:18 | *v1 | consts.cpp:115:21:115:22 | *v2 | provenance | |
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| consts.cpp:115:21:115:22 | *v2 | consts.cpp:116:9:116:13 | *access to array | provenance | |
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| consts.cpp:115:21:115:22 | *v2 | consts.cpp:120:2:120:11 | *... = ... | provenance | |
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| consts.cpp:115:17:115:18 | *v1 | consts.cpp:115:21:115:22 | *{...} | provenance | |
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| consts.cpp:115:21:115:22 | *{...} | consts.cpp:116:9:116:13 | *access to array | provenance | |
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| consts.cpp:115:21:115:22 | *{...} | consts.cpp:120:2:120:11 | *... = ... | provenance | |
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| consts.cpp:120:2:120:11 | *... = ... | consts.cpp:121:9:121:10 | *v8 | provenance | |
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| consts.cpp:123:2:123:12 | *... = ... | consts.cpp:24:7:24:9 | **gv1 | provenance | |
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| consts.cpp:129:19:129:20 | *v1 | consts.cpp:130:9:130:10 | *v9 | provenance | |
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nodes
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| consts.cpp:24:7:24:9 | **gv1 | semmle.label | **gv1 |
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| consts.cpp:25:2:25:4 | *a | semmle.label | *a |
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| consts.cpp:26:2:26:4 | *b | semmle.label | *b |
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| consts.cpp:26:2:26:4 | *{...} | semmle.label | *{...} |
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| consts.cpp:29:7:29:25 | **nonConstFuncToArray | semmle.label | **nonConstFuncToArray |
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| consts.cpp:30:9:30:14 | *access to array | semmle.label | *access to array |
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| consts.cpp:85:7:85:8 | gets output argument | semmle.label | gets output argument |
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| consts.cpp:111:7:111:13 | *call to varFunc | semmle.label | *call to varFunc |
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| consts.cpp:112:9:112:10 | *v6 | semmle.label | *v6 |
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| consts.cpp:115:17:115:18 | *v1 | semmle.label | *v1 |
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| consts.cpp:115:21:115:22 | *v2 | semmle.label | *v2 |
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| consts.cpp:115:21:115:22 | *{...} | semmle.label | *{...} |
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| consts.cpp:116:9:116:13 | *access to array | semmle.label | *access to array |
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| consts.cpp:120:2:120:11 | *... = ... | semmle.label | *... = ... |
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| consts.cpp:121:9:121:10 | *v8 | semmle.label | *v8 |

‎cpp/ql/test/query-tests/Security/CWE/CWE-319/UseOfHttp/UseOfHttp.expected

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| test.cpp:28:10:28:29 | *http://example.com | test.cpp:11:26:11:28 | *url | provenance | |
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| test.cpp:35:23:35:42 | *http://example.com | test.cpp:35:23:35:42 | *http://example.com | provenance | |
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| test.cpp:35:23:35:42 | *http://example.com | test.cpp:39:11:39:15 | *url_l | provenance | |
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| test.cpp:36:26:36:45 | *http://example.com | test.cpp:36:26:36:45 | *http://example.com | provenance | |
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| test.cpp:36:26:36:45 | *http://example.com | test.cpp:40:11:40:17 | *access to array | provenance | |
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| test.cpp:36:26:36:45 | *http://example.com | test.cpp:36:26:36:45 | *{...} | provenance | |
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| test.cpp:36:26:36:45 | *{...} | test.cpp:40:11:40:17 | *access to array | provenance | |
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| test.cpp:38:11:38:15 | *url_g | test.cpp:11:26:11:28 | *url | provenance | |
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| test.cpp:39:11:39:15 | *url_l | test.cpp:11:26:11:28 | *url | provenance | |
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| test.cpp:40:11:40:17 | *access to array | test.cpp:11:26:11:28 | *url | provenance | |
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| test.cpp:35:23:35:42 | *http://example.com | semmle.label | *http://example.com |
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| test.cpp:35:23:35:42 | *http://example.com | semmle.label | *http://example.com |
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| test.cpp:36:26:36:45 | *http://example.com | semmle.label | *http://example.com |
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| test.cpp:36:26:36:45 | *http://example.com | semmle.label | *http://example.com |
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| test.cpp:36:26:36:45 | *{...} | semmle.label | *{...} |
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| test.cpp:38:11:38:15 | *url_g | semmle.label | *url_g |
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| test.cpp:39:11:39:15 | *url_l | semmle.label | *url_l |
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| test.cpp:40:11:40:17 | *access to array | semmle.label | *access to array |

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