X86_64: silence some truncation warnings #76
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fischman-bcny
approved these changes
Jul 13, 2023
|
I like that idea - I wonder if they will get a bit too repetitive, but I can see if I can add them appropriately. Would be nice to get a second pair of eyes to verify that these are indeed safe (which I believe them to be). |
There are a number of places where we truncate to a 32-bit value from a 64-bit value as we may running a 32-bit binary on 64-bits. This silences some of the warnings by explicitly truncating the integers rather than implicitly performing the operation.
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fischman-bcny
approved these changes
Jul 14, 2023
| gp.es = regs[21]; | ||
| gp.fs = regs[22]; | ||
| gp.gs = regs[23]; | ||
| // Truncate the value to 32-bit as these are 32-bit registers. |
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I guess I'm a bit confused about the point of CPUState64 being a union. Why not simply
memcpy(gp.regs, regs, sizeof(gp.regs));
and avoid the need to remember which of these need to be truncated, etc?
| @@ -594,7 +595,7 @@ struct CPUState { | |||
| } | |||
| inline void setPC(uint64_t pc) { | |||
| if (is32) | |||
| state32.setPC(pc); | |||
| state32.setPC(static_cast<uint32_t>(pc)); | |||
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As mentioned in slack, IMO better to have a helper like
// When debugging a 32-bit inferior on a 64-bit platform registers etc frequently need truncation to 32-bits with an assumption that the high bits are zero. This helper does the cast and asserts no information is lost in the process.
static inline truncate64To32Losslessly(uint64_t data) {
DS2ASSERT(data >> 32 == 0 && "64-bit value being truncated to 32-bits has non-zero high word");
return static_cast<uint32_t>(data);
}
| @@ -193,7 +193,7 @@ int HardwareBreakpointManager::hit(Target::Thread *thread, Site &site) { | |||
| if (debugRegs[kStatusRegIdx] & (1ull << i)) { | |||
| DS2ASSERT(_locations[i] != 0); | |||
| site = _sites.find(_locations[i])->second; | |||
| regIdx = i; | |||
| regIdx = static_cast<int>(i); | |||
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simpler to s/size_t/int/ at l.192?
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There are a number of places where we truncate to a 32-bit value from a 64-bit value as we may running a 32-bit binary on 64-bits. This silences some of the warnings by explicitly truncating the integers rather than implicitly performing the operation.