[Buildroot] [PATCH] package/lshw: fix musl build

[Yann E. MORIN <yann.morin.1998@free.fr>]

Romain, Khem, All,

On 2016-08-04 21:25 -0700, Khem Raj spake thusly:
> On 8/4/16 9:37 AM, Thomas Petazzoni wrote:
> > Hello,
> > 
> > On Thu,  4 Aug 2016 18:24:46 +0200, Romain Naour wrote:
> > 
> >> +diff --git a/src/core/dasd.cc b/src/core/dasd.cc
> >> +index 626b8a8..18d19c3 100644
> >> +--- a/src/core/dasd.cc
> >> ++++ b/src/core/dasd.cc
> >> +@@ -4,6 +4,7 @@
> >> + #include <glob.h>
> >> + #include <string.h>
> >> + #include <fcntl.h>
> >> ++#include <libgen.h>
> > 
> > Is this related?
> 
> if we want to use POSIX compliant version of basename() then we need to
> include this yes.

Confirmed. ;-)

> >> + #include <unistd.h>
> >> + #include <inttypes.h>
> >> + #include <sys/ioctl.h>
> >> +@@ -42,7 +43,7 @@ bool scan_dasd(hwNode & n)
> >> +   {
> >> +     for(dev_num=0;dev_num<devices.gl_pathc;dev_num++)
> >> +     {
> >> +-      dev_name = basename(devices.gl_pathv[dev_num]);
> >> ++      dev_name = basename(const_cast<char *>(devices.gl_pathv[dev_num]));
> > 
> > I'm not super familiar with C++ stuff, but why is this problem musl
> > specific? The basename() function is "char *basename(char *)"
> > regardless of the C library being used. What makes it error out with
> > musl and not with other C libraries?
> 
> glibc and uclibc implement the GNU version of basename() API which does
> not modify the argument ( const char*) and when including string.h and
> not libgen.h we are saying we want gnu version. musl does not implement
> the gnu extention, it only has POSIX version. Hence you see the issue
> just on musl.
> 
> So the patch makes it compile for all libcs. however, it should be
> tested on glibc/uclibc since there were bugs in the posix implementation
> of basename()  see
> 
> http://man7.org/linux/man-pages/man3/basename.3.html
> 
> if it cant be tested then make the posix version use only for musl
> which I would not recommend, but its an option

Note however that upstream already did a similar change in an other
file (src/core/pci.cc, by the end of the commit):
    https://github.com/lyonel/lshw/commit/cd690bff1516b40fecd5ec4a7f6619e5bffc3cf0

Romain did open a pull request, but it has not yet been merged:
    https://github.com/lyonel/lshw/pull/17

However, I believe casting is utterly wrong: c_str() returns a
const char* and C++98 states that that string must *not* be modified,
but the POSIX basename() *does* modify its argument.

So, I really believe that the correct fix is completely different
(abstracting away basename, maybe?).

Regards,
Yann E. MORIN.

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