CI: build examples for additional code verification

[mback2k]

Some CIs already build them, let's do it on more of them.

Follow up to #7690
Replaces #7591

[mback2k]

Is Circle CI actually running for PRs? I can't find it in the listing below or am I just blind? @bagder

[mback2k]

Quoting @jay from #7591 (comment) for further discussion:

do you have any idea why the examples using fprintf cannot compile on the failed Azure DevOps builds?

It looks like warnings are treated as errors but I don't know why it's an error for just the examples. I found this post from you many years ago, and maybe we can get around it with -Wno-pedantic-ms-format

Thanks. I just checked and found that -Wno-pedantic-ms-format is actually being used to build the examples. The error message is also a little different this time:

2021-10-29T20:45:35.3132082Z depbase=`echo anyauthput.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
2021-10-29T20:45:35.3137364Z i686-w64-mingw32-gcc -DHAVE_CONFIG_H   -I../../include -DCURL_NO_OLDIES  -isystem C:/msys64/mingw32/include -isystem C:/msys64/mingw32/include -isystem C:/msys64/mingw32/include  -Werror-implicit-function-declaration -g -O0 -pedantic -Wall -W -Wpointer-arith -Wwrite-strings -Wunused -Wshadow -Winline -Wnested-externs -Wmissing-declarations -Wmissing-prototypes -Wno-long-long -Wbad-function-cast -Wfloat-equal -Wno-multichar -Wsign-compare -Wundef -Wno-format-nonliteral -Wendif-labels -Wstrict-prototypes -Wdeclaration-after-statement -Wold-style-definition -Wstrict-aliasing=3 -Wcast-align -Wtype-limits -Wold-style-declaration -Wmissing-parameter-type -Wempty-body -Wclobbered -Wignored-qualifiers -Wconversion -Wno-sign-conversion -Wvla -ftree-vrp -Wno-pedantic-ms-format -Wdouble-promotion -Wformat=2 -Warray-bounds=2 -Wshift-negative-value -Wshift-overflow=2 -Wnull-dereference -fdelete-null-pointer-checks -Wduplicated-cond -Wunused-const-variable -Wduplicated-branches -Wrestrict -Walloc-zero -Wformat-overflow=2 -Wformat-truncation=2 -Wimplicit-fallthrough=4 -Wno-system-headers -Wenum-conversion -Werror -pedantic-errors -MT anyauthput.o -MD -MP -MF $depbase.Tpo -c -o anyauthput.o anyauthput.c &&\
2021-10-29T20:45:35.3148223Z mv -f $depbase.Tpo $depbase.Po

2021-10-29T20:45:36.3328869Z anyauthput.c: In function 'read_callback':
2021-10-29T20:45:36.3329906Z anyauthput.c:93:19: error: ISO C does not support the 'I' printf flag [-Werror=format=]
2021-10-29T20:45:36.3330688Z    93 |   fprintf(stderr, "*** We read %" CURL_FORMAT_CURL_OFF_T
2021-10-29T20:45:36.3331692Z       |                   ^~~~~~~~~~~~~~~
2021-10-29T20:45:36.3332535Z anyauthput.c:93:19: error: format '%d' expects argument of type 'int', but argument 3 has type 'curl_off_t' {aka 'long long int'} [-Werror=format=]
2021-10-29T20:45:36.3334204Z In file included from ../../include/curl/curl.h:35,
2021-10-29T20:45:36.3334847Z                  from anyauthput.c:32:
2021-10-29T20:45:36.3335536Z ../../include/curl/system.h:199:42: note: format string is defined here
2021-10-29T20:45:36.3336240Z   199 | #  define CURL_FORMAT_CURL_OFF_T     "I64d"
2021-10-29T20:45:36.3949522Z cc1.exe: all warnings being treated as errors
2021-10-29T20:45:36.4188318Z make[2]: *** [Makefile:1813: anyauthput.o] Error 1
2021-10-29T20:45:36.4189142Z make[2]: *** Waiting for unfinished jobs....
2021-10-29T20:45:36.6744255Z make[2]: Leaving directory '/c/__w/1/s/docs/examples'
2021-10-29T20:45:36.6756852Z make[1]: *** [Makefile:1928: check-am] Error 2
2021-10-29T20:45:36.6759935Z make[1]: Leaving directory '/c/__w/1/s/docs/examples'
2021-10-29T20:45:36.6848015Z make: *** [Makefile:1741: examples] Error 2
2021-10-29T20:45:36.7881488Z ##[error]Cmd.exe exited with code '2'.
2021-10-29T20:45:36.8831887Z ##[section]Finishing: compile

So the error message mentions '%d' , but then points to a definition of CURL_FORMAT_CURL_OFF_T as "I64d".

I think something is off with how the typedef's are done if used from the examples. This looks like a mismatch to me.

[mback2k]

Another interesting find: the error message does not appear in the Cirrus Windows builds which are using the same Docker images as the Azure Windows builds, therefore use the identical toolchain. The only difference is that the Cirrus Windows builds are release and not debug builds.

[jay]

This looks like #6079, which was solved by ignoring -Wformat. If it's a bug in gcc 10 then one of us should report it. I don't have mingw-w64 gcc 10 but I just tried mingw-w64 gcc 9 and I don't get the error unless I exclude -Wno-pedantic-ms-format.

[mback2k]

Thanks for digging this up @jay. Let's see what happens if I put the same workaround into the examples, although I am still wondering why the Cirrus CI builds are not affected without it.

It also looks like this is mostly affecting external code, because curl internal code mostly uses the curlx_* versions of printf*. For example tool_writeout.c uses curlx as a workaround while tool_filetime.c uses @bagder's pragma-based workaround. I guess a follow up PR could be to make tool_filetime.c also use curlx instead, right?

[mback2k]

Regarding the follow up PR mentioned above. I just created a draft one, since the pragma is now obsolete due to #6535.

[mback2k]

@bagder I don't have the time now, but you may wanna investigate this error that shows up in AppVeyor for master and this PR:

3>c:\projects\curl\src\tool_operate.c(889) : error C2220: warning treated as error - no 'object' file generated
3>c:\projects\curl\src\tool_operate.c(889) : warning C4701: potentially uninitialized local variable 'per' use

[mback2k]

@bagder please confirm with another approval if you are fine with adding the pragma to the relevant examples, thanks.

[bagder]

I think the added pragma lines are unfortunate since the examples are meant to contain as little "extra fluff" as possible. I assume you haven't figured out any other way to work around the problems you get without them? Can we remove/change the printf lines instead?

[mback2k]

@bagder I just tried to update the relevant printf lines by using unsigned long instead of curl_off_t.

[mback2k]

Rebased again after @bagder simplified progressfunc.c with e75bc3a.