diff options
| author | Vasil Dimov <vd@FreeBSD.org> | 2020-05-01 14:05:48 +0200 |
|---|---|---|
| committer | Vasil Dimov <vd@FreeBSD.org> | 2020-05-03 17:21:45 +0200 |
| commit | 71f183a49b714a28622277fa668d8f9f3dac0aae (patch) | |
| tree | 34c61e4835aff14a38eec1982777a6a6ec47a890 /src | |
| parent | ddc0a600b38ac6cef044085cdee46649fc437562 (diff) | |
build: warn on potentially uninitialized reads
Enable -Wconditional-uninitialized to warn on potentially uninitialized
reads.
Fix the sole such warning in Bitcoin Core in GetRdRand(): r1 would be
set to 0 on rdrand failure, so initializing it to 0 is a non-functional
change.
From "Intel 64 and IA-32 ArchitecturesSoftware Developer's Manual" [1],
page 1711: "CF=1 indicates that the data in the destination is valid.
Otherwise CF=0 and the data in the destination operand will be returned
as zeros for the specified width."
[1] https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf
Diffstat (limited to 'src')
| -rw-r--r-- | src/Makefile.leveldb.include | 2 | ||||
| -rw-r--r-- | src/random.cpp | 7 |
2 files changed, 6 insertions, 3 deletions
diff --git a/src/Makefile.leveldb.include b/src/Makefile.leveldb.include index 04b53471e4..79ff72ca8d 100644 --- a/src/Makefile.leveldb.include +++ b/src/Makefile.leveldb.include @@ -36,7 +36,7 @@ LEVELDB_CPPFLAGS_INT += -DLEVELDB_PLATFORM_POSIX endif leveldb_libleveldb_a_CPPFLAGS = $(AM_CPPFLAGS) $(LEVELDB_CPPFLAGS_INT) $(LEVELDB_CPPFLAGS) -leveldb_libleveldb_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS) +leveldb_libleveldb_a_CXXFLAGS = $(filter-out -Wconditional-uninitialized -Werror=conditional-uninitialized, $(AM_CXXFLAGS)) $(PIE_FLAGS) leveldb_libleveldb_a_SOURCES= leveldb_libleveldb_a_SOURCES += leveldb/port/port_stdcxx.h diff --git a/src/random.cpp b/src/random.cpp index b408b1e13e..5b8782d1ce 100644 --- a/src/random.cpp +++ b/src/random.cpp @@ -116,7 +116,10 @@ static uint64_t GetRdRand() noexcept // RdRand may very rarely fail. Invoke it up to 10 times in a loop to reduce this risk. #ifdef __i386__ uint8_t ok; - uint32_t r1, r2; + // Initialize to 0 to silence a compiler warning that r1 or r2 may be used + // uninitialized. Even if rdrand fails (!ok) it will set the output to 0, + // but there is no way that the compiler could know that. + uint32_t r1 = 0, r2 = 0; for (int i = 0; i < 10; ++i) { __asm__ volatile (".byte 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r1), "=q"(ok) :: "cc"); // rdrand %eax if (ok) break; @@ -128,7 +131,7 @@ static uint64_t GetRdRand() noexcept return (((uint64_t)r2) << 32) | r1; #elif defined(__x86_64__) || defined(__amd64__) uint8_t ok; - uint64_t r1; + uint64_t r1 = 0; // See above why we initialize to 0. for (int i = 0; i < 10; ++i) { __asm__ volatile (".byte 0x48, 0x0f, 0xc7, 0xf0; setc %1" : "=a"(r1), "=q"(ok) :: "cc"); // rdrand %rax if (ok) break; |