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2 fixes for rt.backtrace.dwarf #2151

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thewilsonator merged 1 commit into from
Apr 15, 2019
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2 fixes for rt.backtrace.dwarf #2151

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35 changes: 24 additions & 11 deletions src/rt/backtrace/dwarf.d
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Original file line number Diff line number Diff line change
Expand Up @@ -79,31 +79,44 @@ int traceHandlerOpApplyImpl(const void*[] callstack, scope int delegate(ref size
int ret = 0;
foreach (size_t i; 0 .. callstack.length)
{
char[1536] buffer = void; buffer[0] = 0;
char[256] addressBuffer = void; addressBuffer[0] = 0;
char[1536] buffer = void;
size_t bufferLength = 0;

void appendToBuffer(Args...)(const(char)* format, Args args)
{
const count = snprintf(buffer.ptr + bufferLength, buffer.length - bufferLength, format, args);
assert(count >= 0);
bufferLength += count;
if (bufferLength >= buffer.length)
bufferLength = buffer.length - 1;
}

if (locations.length > 0 && locations[i].line != -1)
snprintf(addressBuffer.ptr, addressBuffer.length, "%.*s:%d ", cast(int) locations[i].file.length, locations[i].file.ptr, locations[i].line);
{
appendToBuffer("%.*s:%d ", cast(int) locations[i].file.length, locations[i].file.ptr, locations[i].line);
}
else
addressBuffer[] = "??:? \0";
{
buffer[0 .. 5] = "??:? ";
bufferLength = 5;
}
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@kinke kinke Mar 25, 2018

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Fix 1:

addressBuffer[] = "??:? \0";

=> object.Error@(0): Array lengths don't match for copy https://run.dlang.io/is/4RQZWh

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@wilzbach wilzbach Mar 25, 2018

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Any chance we can add a test for this to prevent future regressions?

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@kinke kinke Mar 25, 2018

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It's pretty bad with -release, causing a segfault as long as the destination buffer is sufficiently large: https://run.dlang.io/is/NEqZOB. Without -release an exception is thrown during stacktrace generation, which is also pretty bad.

The latter is how I stumbled on this. LLVM 6.0 led to DWARF v4 debuginfos, rt.backtrace.dwarf doesn't support that version, so no file/line infos => "??:? \0" + exception (debug druntime only; release druntime compiled with -release happily reads beyond the string constant, causing no segfault on x86 apparently). The exception with debug-druntime is swallowed in my test case, it only manifests itself in an incomplete stack trace (single entry).

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@kinke kinke Apr 3, 2018

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@wilzbach: There's no debug druntime (i.e., compiled with enabled bounds checks) available for CI, right? Then it's untestable.


char[1024] symbolBuffer = void;
int bufferLength;
auto symbol = getDemangledSymbol(frameList[i][0 .. strlen(frameList[i])], symbolBuffer);
if (symbol.length > 0)
bufferLength = snprintf(buffer.ptr, buffer.length, "%s%.*s ", addressBuffer.ptr, cast(int) symbol.length, symbol.ptr);
else
bufferLength = snprintf(buffer.ptr, buffer.length, "%s", addressBuffer.ptr);
appendToBuffer("%.*s ", cast(int) symbol.length, symbol.ptr);

assert(bufferLength >= 0);
const addressLength = 20;
const maxBufferLength = buffer.length - addressLength;
if (bufferLength > maxBufferLength)
{
buffer[maxBufferLength-4 .. maxBufferLength] = "... ";
bufferLength = maxBufferLength;
buffer[$-4-addressLength..$-addressLength] = "... ";
}
bufferLength += snprintf(buffer.ptr + bufferLength, buffer.length, "[0x%x]", callstack[i]);
static if (size_t.sizeof == 8)
appendToBuffer("[0x%llx]", callstack[i]);
else
appendToBuffer("[0x%x]", callstack[i]);
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@kinke kinke Mar 25, 2018 •
edited
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Fix 2: don't restrict to lower 32 bits of address on 64-bit platforms, e.g., now ??:? __libc_start_main [0x7f7bb141182f].


auto output = buffer[0 .. bufferLength];
auto pos = i;
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