On 5 July 2017 at 14:09, Melanie Blower via Phabricator < revi...@reviews.llvm.org> wrote:
> mibintc added a comment. > > Jonas asked about adding a new test to ensure that "-include > stdc-predef.h" does not get added if the file doesn't exist. > > I added a reply to that but I can't see where it went. So I'm writing the > reply again. > > The current version of the patch doesn't check for the existence of > stdc-predef.h. As far as I understand, this is consistent with gcc > behavior. It is expected that if you are on a system without stdc-predef.h > then you can add -ffreestanding. > That does not seem reasonable. Plenty of libc implementations exist that don't provide this header. GCC might want to strongly express a preference for glibc, but we don't. > In a prior revision of this patch (see Diff 4), I attempted to iterate > through the system directories to check for the existence of the file > before adding -include with a full path name. However that patch didn't > work. I was using this call to iterate through the system includes: > getAllArgValues(options::OPT_isystem). However, the directory where > stdc-predef.h is located, /usr/include, is added into the search path by > using the option -internal-externc-isystem. > getAllArgValues(options::OPT_isystem) > does not iterate through the include directories which were added via > -internal-externc-isystem. [Note: is this a bug?]. There is no enumeration > value within options::OPT_? which corresponds to -internal-externc-isystem. > > I could check for the existence of this file: /usr/include/stdc-predef.h; > I don't know whether this would be acceptable or if it's correct. Trying to fake up headers search from the driver doesn't sound like a good way forward. Perhaps instead you could add a -include-if-exists flag to -cc1 for this purpose, where -include-if-exists X would expand to something like #if __has_include(X) #include X #endif
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