[cmake] Add -Wcast-qual to C flags if LLVM_ENABLE_WARNINGS is defined.

[AlexM]

Summary

Disable this warning for specific cast in llvm_regcomp().

[dblaikie]

Sounds good to me

llvm/cmake/modules/HandleLLVMOptions.cmake

744

looks like in other cases C_FLAGS comes before CXX_FLAGS - maybe switch this around for consistency?

[AlexM]

switch C_FLAGS and CXX_FLAGS

[AlexM]

Fixed. @dblaikie could you please commit this on my behalf?

[AlexM]

@dblaikie ping

[chapuni]

@AlexM @dblaikie Could you take care of c-index-test.c?

[MaskRay]

In D153911#4513152, @chapuni wrote:

@AlexM @dblaikie Could you take care of c-index-test.c?

I saw the warning as well. See D155670 :)

[DavidSpickett]

Another fix for libunwind 32 bit builds: https://reviews.llvm.org/D155685

[hctim]

Hi, we're still seeing sanitizer buildbot failures from what I assume is this patch.

https://lab.llvm.org/buildbot/#/builders/37/builds/23724

/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/profile/InstrProfilingValue.c:62:17: error: cast from 'const unsigned short *' to 'unsigned short *' drops const qualifier [-Werror,-Wcast-qual]
   62 |   *((uint16_t *)&Data->NumValueSites[ValueKind]) = NumValueSites;

Maybe it's worth reverting, doing the cleanup, and then re-submitting rather than trying to fix-forward? It would appear if there's a lot of cleanup required.

[AlexM]

In D153911#4514140, @hctim wrote:

Hi, we're still seeing sanitizer buildbot failures from what I assume is this patch.

https://lab.llvm.org/buildbot/#/builders/37/builds/23724

/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/profile/InstrProfilingValue.c:62:17: error: cast from 'const unsigned short *' to 'unsigned short *' drops const qualifier [-Werror,-Wcast-qual]
   62 |   *((uint16_t *)&Data->NumValueSites[ValueKind]) = NumValueSites;

Maybe it's worth reverting, doing the cleanup, and then re-submitting rather than trying to fix-forward? It would appear if there's a lot of cleanup required.

I do not have commit access, but I think reverting this makes sense if it is causing build failures. Sorry for the inconvenience!

[MaskRay]

In D153911#4515057, @AlexM wrote:

In D153911#4514140, @hctim wrote:

Hi, we're still seeing sanitizer buildbot failures from what I assume is this patch.

https://lab.llvm.org/buildbot/#/builders/37/builds/23724

/b/sanitizer-x86_64-linux/build/llvm-project/compiler-rt/lib/profile/InstrProfilingValue.c:62:17: error: cast from 'const unsigned short *' to 'unsigned short *' drops const qualifier [-Werror,-Wcast-qual]
   62 |   *((uint16_t *)&Data->NumValueSites[ValueKind]) = NumValueSites;

Maybe it's worth reverting, doing the cleanup, and then re-submitting rather than trying to fix-forward? It would appear if there's a lot of cleanup required.

I do not have commit access, but I think reverting this makes sense if it is causing build failures. Sorry for the inconvenience!

compiler-rt/lib/profile has been fixed by commit 51c8cacafd47b59e66816b10be357a9877187bc3.

[RKSimon]

llvm/lib/Support/regcomp.c

337

@AlexM We're still seeing Wcast-qual warnings on clang-cl builds - please can you take a look?

llvm/cmake/modules/HandleLLVMOptions.cmake

if (LLVM_ENABLE_WARNINGS AND (LLVM_COMPILER_IS_GCC_COMPATIBLE OR CLANG_CL))
 
   # Don't add -Wall for clang-cl, because it maps -Wall to -Weverything for
   # MSVC compatibility.  /W4 is added above instead.
   if (NOT CLANG_CL)
     append("-Wall" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
   endif()
 
   append("-Wextra -Wno-unused-parameter -Wwrite-strings" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
-  append("-Wcast-qual" CMAKE_CXX_FLAGS)
+  append("-Wcast-qual" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
   # Turn off missing field initializer warnings for gcc to avoid noise from
   # false positives with empty {}. Turn them on otherwise (they're off by
   # default for clang).
   check_cxx_compiler_flag("-Wmissing-field-initializers" CXX_SUPPORTS_MISSING_FIELD_INITIALIZERS_FLAG)
   if (CXX_SUPPORTS_MISSING_FIELD_INITIALIZERS_FLAG)
     if (CMAKE_COMPILER_IS_GNUCXX)
       append("-Wno-missing-field-initializers" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)

llvm/lib/Support/regcomp.c

#endif
   p->slen = 0;
   if (p->strip == NULL) {
     free((char *)g);
     return(REG_ESPACE);
   }
 
   /* set things up */
   p->g = g;
+  /* suppress warning from the following explicit cast. */
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-qual"
+#endif /* __GNUC__ */
   p->next = (char *)pattern;  /* convenience; we do not modify it */
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif /* __GNUC__ */
   p->end = p->next + len;
   p->error = 0;
   p->ncsalloc = 0;
   for (i = 0; i < NPAREN; i++) {
     p->pbegin[i] = 0;
     p->pend[i] = 0;
   }
   g->csetsize = NC;