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ws: -Wtype-limits warning in ws_payload_remain() #19017
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- changed the title
[-]ws: `-Wtype-limits` warning in `ws_payload_remain`[/-][+]ws: `-Wtype-limits` warning in `ws_payload_remain()`[/+]on Oct 11, 2025 lib/ws.c:658:35: error: comparison is always false due to limited range of data type [-Werror=type-limits]
What is
curl_off_ton this machine? I think it needs to be a signed type and then I can't understand why this warns!It should be a long long according to system.h. I could not spot a platform where it's unsigned. Found the warning odd also. (Haven't run this build locally yet)
We could try to rewrite it to avoid the typecast:
diff --git a/lib/ws.c b/lib/ws.c index 6c8f07e177..fa6602a152 100644 --- a/lib/ws.c +++ b/lib/ws.c @@ -653,11 +653,11 @@ static curl_off_t ws_payload_remain(curl_off_t payload_total, { curl_off_t remain = payload_total - payload_offset; if((payload_total < 0) || (payload_offset < 0) || (remain < 0)) return -1; #if SIZEOF_OFF_T <= SIZEOF_SIZE_T - if((curl_off_t)payload_buffered < 0) + if(payload_buffered > SIZE_MAX/2) return -1; #endif if(remain < (curl_off_t)payload_buffered) return -1; return remain - (curl_off_t)payload_buffered;
It's implementation defined to cast an unsigned type to a signed if it doesn't fit. So for all we know this compiler will set a too large positive number to something positive like 0 or fffff whatever, which is unusual, but OTOH we're compiling for DOS
and I don't know where else that warning would come from.Regardless the guard looks wrong because curl_off_t is never less than 8 bytes anywhere, so the check shouldn't be against SIZEOF_OFF_T but rather SIZEOF_CURL_OFF_T. As it happens once that is fixed it would never be true for DOS or Windows targets because
#if 8 <= 4is false so payload_buffered should always fit in a curl_off_t#if SIZEOF_CURL_OFF_T <= SIZEOF_SIZE_T if(payload_buffered > (size_t)CURL_OFF_T_MAX) return -1; #endif
edit: Well I should have figured this out half an hour ago when I posted but I think that warning comes because the guard was wrong so "limited range of data type" is true in that the size_t always fits in the curl_off_t.
I did this
Built curl for MS-DOS in CI, where the build reaches this line due to
SIZEOF_OFF_T <= SIZEOF_SIZE_T(4 <= 4):https://github.com/curl/curl/actions/runs/18420572155/job/52493664744?pr=18039#step:9:27
Ref: a4d3c4e #18965
I expected the following
Clean build.
curl/libcurl version
master
operating system
MS-DOS (maybe others with SIZEOF_OFF_T <= SIZEOF_SIZE_T)