[PATCH] D10431: PR21174 - clang only searches current working directory for precompiled include file

Mon Aug 17 09:24:43 PDT 2015

thakis added a subscriber: thakis.

================
Comment at: lib/Driver/Tools.cpp:398
@@ +397,3 @@
+              FoundPTH = !UsePCH;
+            }
+          }
----------------
kimgr wrote:
> kimgr wrote:
> > kimgr wrote:
> > > kimgr wrote:
> > > > Add a `break;` here so we don't continue searching after a valid path has been found
> > > The GCC docs here [1] say:
> > > 
> > >     If not found there, it is searched for in the remainder of the #include "..." search chain as normal.
> > > 
> > > I can't tell if the quotes are significant and if they mean only -I is searched. I don't have a GCC environment currently to test with.
> > > 
> > > [1] https://gcc.gnu.org/onlinedocs/gcc-4.9.3/gcc/Preprocessor-Options.html#index-nostdinc_002b_002b-1026
> > I found a FreeBSD machine and set up GCC. I had to adjust the repro case to use `truss` instead of `strace`, so I hope I didn't mess anything up.
> > 
> > I removed the rule generating the .gch file, so GCC would have to keep searching and it appears to be following the entire include search path, including system paths. Trace below:
> > 
> > ...
> > 30860: stat("./precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("./precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: stat("./build/include/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("./build/include/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: stat("./include/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("./include/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local",{ mode=drwxr-xr-x ,inode=115,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib",{ mode=drwxr-xr-x ,inode=16476,size=1318,blksize=84480 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48",{ mode=drwxr-xr-x ,inode=24335,size=66,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include",{ mode=drwxr-xr-x ,inode=24336,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++",{ mode=drwxr-xr-x ,inode=24337,size=98,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/lib/gcc48/include/c++/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/local/lib/gcc48/include/c++/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local",{ mode=drwxr-xr-x ,inode=115,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib",{ mode=drwxr-xr-x ,inode=16476,size=1318,blksize=84480 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48",{ mode=drwxr-xr-x ,inode=24335,size=66,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include",{ mode=drwxr-xr-x ,inode=24336,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++",{ mode=drwxr-xr-x ,inode=24337,size=98,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++/x86_64-portbld-freebsd10.1",{ mode=drwxr-xr-x ,inode=21305,size=4,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++/x86_64-portbld-freebsd10.1/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/lib/gcc48/include/c++//x86_64-portbld-freebsd10.1/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/local/lib/gcc48/include/c++//x86_64-portbld-freebsd10.1/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local",{ mode=drwxr-xr-x ,inode=115,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib",{ mode=drwxr-xr-x ,inode=16476,size=1318,blksize=84480 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48",{ mode=drwxr-xr-x ,inode=24335,size=66,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include",{ mode=drwxr-xr-x ,inode=24336,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++",{ mode=drwxr-xr-x ,inode=24337,size=98,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++/backward",{ mode=drwxr-xr-x ,inode=21290,size=10,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/include/c++/backward/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/lib/gcc48/include/c++//backward/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/local/lib/gcc48/include/c++//backward/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local",{ mode=drwxr-xr-x ,inode=115,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib",{ mode=drwxr-xr-x ,inode=16476,size=1318,blksize=84480 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48",{ mode=drwxr-xr-x ,inode=24335,size=66,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc",{ mode=drwxr-xr-x ,inode=145103,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1",{ mode=drwxr-xr-x ,inode=145104,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4",{ mode=drwxr-xr-x ,inode=145105,size=16,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include",{ mode=drwxr-xr-x ,inode=145106,size=64,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local",{ mode=drwxr-xr-x ,inode=115,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local/include",{ mode=drwxr-xr-x ,inode=16474,size=218,blksize=14336 }) = 0 (0x0)
> > 30860: lstat("/usr/local/include/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/include/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/local/include/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local",{ mode=drwxr-xr-x ,inode=115,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib",{ mode=drwxr-xr-x ,inode=16476,size=1318,blksize=84480 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48",{ mode=drwxr-xr-x ,inode=24335,size=66,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc",{ mode=drwxr-xr-x ,inode=145103,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1",{ mode=drwxr-xr-x ,inode=145104,size=3,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4",{ mode=drwxr-xr-x ,inode=145105,size=16,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include-fixed",{ mode=drwxr-xr-x ,inode=145194,size=12,blksize=131072 }) = 0 (0x0)
> > 30860: lstat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include-fixed/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include-fixed/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/local/lib/gcc48/gcc/x86_64-portbld-freebsd10.1/4.8.4/include-fixed/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: lstat("/usr",{ mode=drwxr-xr-x ,inode=9,size=16,blksize=4096 }) = 0 (0x0)
> > 30860: lstat("/usr/include",{ mode=drwxr-xr-x ,inode=111,size=307,blksize=19968 }) = 0 (0x0)
> > 30860: lstat("/usr/include/precompiled.header",0x7fffffffd3d8) ERR#2 'No such file or directory'
> > 30860: stat("/usr/include/precompiled.header.gch",0x7fffffffe540) ERR#2 'No such file or directory'
> > 30860: open("/usr/include/precompiled.header",O_NOCTTY,0666) ERR#2 'No such file or directory'
> > 30860: stat("/usr/share/nls/C/libc.cat",0x7fffffffdf18) ERR#2 'No such file or directory'
> > 30860: stat("/usr/share/nls/libc/C",0x7fffffffdf18) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/share/nls/C/libc.cat",0x7fffffffdf18) ERR#2 'No such file or directory'
> > 30860: stat("/usr/local/share/nls/libc/C",0x7fffffffdf18) ERR#2 'No such file or directory'
> > 30860: write(2,"cc1plus: fatal error: precompile"...,68) = 68 (0x44)
> > 30860: write(2,"compilation terminated.\n",24)	 = 24 (0x18)
> > ...
> > 
> So it seems that GCC *does* scan the entire header search path. Unfortunately, that information doesn't seem to be available to the driver (looks to be set up in CompilerInstance::createPreprocessor.
> 
> Should this logic for PCH/PTH scanning move out of the driver and into the frontend?
gcc also checks if the gch file is a directory and if so finds the first file with matching language / defines etc. It also uses gch files for #included files instead of just -included files (https://gcc.gnu.org/onlinedocs/gcc/Precompiled-Headers.html). I thought clang intentionally did none of this so it doesn't have to stat all these directories.

http://reviews.llvm.org/D10431