Bug#822848: mpd FTBFS on Alpha; misaligned arrays in the test suite

Source: mpd Version: 0.19.14-2 Severity: important Justification: fails to build form source (but built in the past) Tags: patch User: debian-alpha@lists.debian.org Usertags: alpha mpd FTBFS on Alpha with a failure in the test suite [1]: FAIL: test/test_byte_reverse ============================ .F... !!!FAILURES!!! Test Results: Run: 4 Failures: 1 Errors: 0 1) test: ByteReverseTest::TestByteReverse2 (F) line: 58 test/test_byte_reverse.cxx assertion failed - Expression: strcmp(result, (const char *)dest) == 0 This occurs because the test suite (in test/test_byte_reversal.cxx) allocates static char arrays and passes the char arrays to functions whose respective arguments were declared to be uint16_t *, etc., in the main code. This is in the realm of undefined behaviour on architectures with strict memory alignment requirements. Although the test only fails on Alpha (because Alpha has a particular CPU load instruction that gcc likes to use to add bugs ..., ahem, optimise the code on the assumption of alignment) it is potentially a latent bug for other architectures with strict alignment requirements. Since the code is compiled with the c++11 standard I attach a patch that modifies the test suite to align the non-compliant strings with the alignas() attribute. The test suite now passes on Alpha with that patch. Cheers Michael [1] https://buildd.debian.org/status/fetch.php?pkg=mpd&arch=alpha&ver=0.19.14-2&stamp=1461542099

Bug#822848: mpd FTBFS on Alpha; misaligned arrays in the test suite
72637d00 · Michael Cree · Max Kellermann · 27d4b159 · 72637d00 · 72637d00
Commit 72637d00 authored Apr 28, 2016 by Michael Cree Committed by Max Kellermann Apr 28, 2016
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NEWS NEWS +1 -0

test_byte_reverse.cxx test/test_byte_reverse.cxx +4 -4

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--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,7 @@ ver 0.19.15 (not yet released)
  - opus: support bigger OpusTags packets
 * fix more build failures on non-glibc builds due to constexpr Mutex
 * fix build failure due to missing include
+* fix unit test on Alpha

 ver 0.19.14 (2016/03/18)
 * decoder

--- a/test/test_byte_reverse.cxx
+++ b/test/test_byte_reverse.cxx
@@ -49,9 +49,9 @@ CPPUNIT_TEST_SUITE_REGISTRATION(ByteReverseTest);
 void
 ByteReverseTest::TestByteReverse2()
 {
-	static const char src[] = "123456";
+	static const char src[] alignas(uint16_t) = "123456";
 	static const char result[] = "214365";
-	static uint8_t dest[ARRAY_SIZE(src)];
+	static uint8_t dest[ARRAY_SIZE(src)] alignas(uint16_t);

 	reverse_bytes(dest, (const uint8_t *)src,
 		      (const uint8_t *)(src + ARRAY_SIZE(src) - 1), 2);
@@ -73,9 +73,9 @@ ByteReverseTest::TestByteReverse3()
 void
 ByteReverseTest::TestByteReverse4()
 {
-	static const char src[] = "12345678";
+	static const char src[] alignas(uint32_t) = "12345678";
 	static const char result[] = "43218765";
-	static uint8_t dest[ARRAY_SIZE(src)];
+	static uint8_t dest[ARRAY_SIZE(src)] alignas(uint32_t);

 	reverse_bytes(dest, (const uint8_t *)src,
 		      (const uint8_t *)(src + ARRAY_SIZE(src) - 1), 4);