[PATCH dwarves v3 9/9] tests: Add a few clang true signature tests

Yonghong Song
2026-03-20T19:10:16Z

Three tests are added.

Test 1: VERBOSE=1 ./clang_parm_optimized.sh
BTF: char * foo(struct t * a, struct t * d);
DWARF: char * foo(struct t * a, int b, struct t * d);
where parameber 'b' is unused.

Test 2: VERBOSE=1 ./clang_parm_optimized_stack.sh
BTF: char * foo(struct t * a, struct t * d);
DWARF: char * foo(struct t * a, int b1, int b2, int b3, int b4, int b5, int b6, struct t * d);
where parameters 'b1' to 'b6' are unused.

Test 3: VERBOSE=1 ./clang_parm_aggregate.sh
BTF: long foo(long a__f1, struct t b, int i);
DWARF: long foo(struct t a, struct t b, int i);
where the 'struct t' definition is 'struct t { long f1; long f2; };', and
a.f2 is not used in the function.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
tests/clang_parm_aggregate.sh | 63 +++++++++++++++++++++++
tests/clang_parm_optimized.sh | 77 +++++++++++++++++++++++++++++
tests/clang_parm_optimized_stack.sh | 77 +++++++++++++++++++++++++++++
3 files changed, 217 insertions(+)
create mode 100755 tests/clang_parm_aggregate.sh
create mode 100755 tests/clang_parm_optimized.sh
create mode 100755 tests/clang_parm_optimized_stack.sh

diff --git a/tests/clang_parm_aggregate.sh b/tests/clang_parm_aggregate.sh
new file mode 100755
index 0000000..bf47c8c
--- /dev/null
+++ b/tests/clang_parm_aggregate.sh
@@ -0,0 +1,63 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+source test_lib.sh
+
+outdir=$(make_tmpdir)
+
+# Comment this out to save test data.
+trap cleanup EXIT
+
+title_log "Validation of BTF encoding of true_signatures."
+
+clang_true="${outdir}/clang_true"
+CC=$(which clang 2>/dev/null)
+
+if [[ -z "$CC" ]]; then
+ info_log "skip: clang not available"
+ test_skip
+fi
+
+cat > ${clang_true}.c << EOF
+struct t { long f1; long f2; };
+__attribute__((noinline)) static long foo(struct t a, struct t b, int i)
+{
+ return a.f1 + b.f1 + b.f2 + i;
+}
+
+struct t p1, p2;
+int i;
+int main()
+{
+ return (int)foo(p1, p2, i);
+}
+EOF
+
+CFLAGS="$CFLAGS -g -O2"
+${CC} ${CFLAGS} -o $clang_true ${clang_true}.c
+if [[ $? -ne 0 ]]; then
+ error_log "Could not compile ${clang_true}.c"
+ test_fail
+fi
+LLVM_OBJCOPY=objcopy pahole -J --btf_features=+true_signature $clang_true
+if [[ $? -ne 0 ]]; then
+ error_log "Could not encode BTF for $clang_true"
+ test_fail
+fi
+
+btf_optimized=$(pfunct --all --format_path=btf $clang_true |grep "foo")
+if [[ -z "$btf_optimized" ]]; then
+ info_log "skip: no optimizations applied."
+ test_skip
+fi
+
+btf_cmp=$btf_optimized
+dwarf=$(pfunct --all $clang_true |grep "foo")
+
+verbose_log "BTF: $btf_optimized DWARF: $dwarf"
+
+if [[ "$btf_cmp" == "$dwarf" ]]; then
+ error_log "BTF and DWARF signatures should be different and they are not: BTF: $btf_optimized ; DWARF $dwarf"
+ test_fail
+fi
+test_pass
diff --git a/tests/clang_parm_optimized.sh b/tests/clang_parm_optimized.sh
new file mode 100755
index 0000000..379e6d5
--- /dev/null
+++ b/tests/clang_parm_optimized.sh
@@ -0,0 +1,77 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+source test_lib.sh
+
+outdir=$(make_tmpdir)
+
+# Comment this out to save test data.
+trap cleanup EXIT
+
+title_log "Validation of BTF encoding of true_signatures."
+
+clang_true="${outdir}/clang_true"
+CC=$(which clang 2>/dev/null)
+
+if [[ -z "$CC" ]]; then
+ info_log "skip: clang not available"
+ test_skip
+fi
+
+cat > ${clang_true}.c << EOF
+struct t { int a; };
+__attribute__((noinline)) char *tar(struct t *a, struct t *d)
+{
+ if (a->a == d->a)
+ return (char *)10;
+ else
+ return (char *)0;
+}
+
+__attribute__((noinline)) static char * foo(struct t *a, int b, struct t *d)
+{
+ return tar(a, d);
+}
+
+__attribute__((noinline)) char *bar(struct t *a, struct t *d)
+{
+ return foo(a, 1, d);
+}
+
+struct t p1, p2;
+int main()
+{
+ return !!bar(&p1, &p2);
+}
+EOF
+
+CFLAGS="$CFLAGS -g -O2"
+${CC} ${CFLAGS} -o $clang_true ${clang_true}.c
+if [[ $? -ne 0 ]]; then
+ error_log "Could not compile ${clang_true}.c"
+ test_fail
+fi
+LLVM_OBJCOPY=objcopy pahole -J --btf_features=+true_signature $clang_true
+if [[ $? -ne 0 ]]; then
+ error_log "Could not encode BTF for $clang_true"
+ test_fail
+fi
+
+btf_optimized=$(pfunct --all --format_path=btf $clang_true |grep "foo")
+if [[ -z "$btf_optimized" ]]; then
+ info_log "skip: no optimizations applied."
+ test_skip
+fi
+
+btf_cmp=$btf_optimized
+dwarf=$(pfunct --all $clang_true |grep "foo")
+
+if [[ -n "$VERBOSE" ]]; then
+ printf " BTF: %s DWARF: %s\n" "$btf_optimized" "$dwarf"
+fi
+
+if [[ "$btf_cmp" == "$dwarf" ]]; then
+ error_log "BTF and DWARF signatures should be different and they are not: BTF: $btf_optimized ; DWARF $dwarf"
+ test_fail
+fi
+test_pass
diff --git a/tests/clang_parm_optimized_stack.sh b/tests/clang_parm_optimized_stack.sh
new file mode 100755
index 0000000..8638af7
--- /dev/null
+++ b/tests/clang_parm_optimized_stack.sh
@@ -0,0 +1,77 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+source test_lib.sh
+
+outdir=$(make_tmpdir)
+
+# Comment this out to save test data.
+trap cleanup EXIT
+
+title_log "Validation of BTF encoding of true_signatures."
+
+clang_true="${outdir}/clang_true"
+CC=$(which clang 2>/dev/null)
+
+if [[ -z "$CC" ]]; then
+ info_log "skip: clang not available"
+ test_skip
+fi
+
+cat > ${clang_true}.c << EOF
+struct t { int a; };
+__attribute__((noinline)) char *tar(struct t *a, struct t *d)
+{
+ if (a->a == d->a)
+ return (char *)10;
+ else
+ return (char *)0;
+}
+
+__attribute__((noinline)) static char * foo(struct t *a, int b1, int b2, int b3, int b4, int b5, int b6, struct t *d)
+{
+ return tar(a, d);
+}
+
+__attribute__((noinline)) char *bar(struct t *a, struct t *d)
+{
+ return foo(a, 1, 2, 3, 4, 5, 6, d);
+}
+
+struct t p1, p2;
+int main()
+{
+ return !!bar(&p1, &p2);
+}
+EOF
+
+CFLAGS="$CFLAGS -g -O2"
+${CC} ${CFLAGS} -o $clang_true ${clang_true}.c
+if [[ $? -ne 0 ]]; then
+ error_log "Could not compile ${clang_true}.c"
+ test_fail
+fi
+LLVM_OBJCOPY=objcopy pahole -J --btf_features=+true_signature $clang_true
+if [[ $? -ne 0 ]]; then
+ error_log "Could not encode BTF for $clang_true"
+ test_fail
+fi
+
+btf_optimized=$(pfunct --all --format_path=btf $clang_true |grep "foo")
+if [[ -z "$btf_optimized" ]]; then
+ info_log "skip: no optimizations applied."
+ test_skip
+fi
+
+btf_cmp=$btf_optimized
+dwarf=$(pfunct --all $clang_true |grep "foo")
+
+if [[ -n "$VERBOSE" ]]; then
+ printf " BTF: %s DWARF: %s\n" "$btf_optimized" "$dwarf"
+fi
+
+if [[ "$btf_cmp" == "$dwarf" ]]; then
+ error_log "BTF and DWARF signatures should be different and they are not: BTF: $btf_optimized ; DWARF $dwarf"
+ test_fail
+fi
+test_pass
--
2.52.0