Hi Alex, On 10/1/20 6:55 PM, Alejandro Colomar wrote: > > > On 2020-10-01 18:38, Michael Kerrisk (man-pages) wrote: >> Hi Alex, >> >>> +According to the C language standard, >>> +a pointer to any object type may be converted to a pointer to >>> +.I void >>> +and back. >>> +POSIX further requires that any pointer, >>> +including pointers to functions, >>> +may be converted to a pointer to >>> +.I void >>> +and back. >> I know you are correct about POSIX, but which part of the >> standard did you find this information in? The only >> reference that I find in POSIX is the dlsym() spec. Is it >> covered also somewhere else in the standrd? >> >> Thanks, >> >> Michael >> > > Hi Michael, > > I've bean searching, and dlsym is the only one: > > ________ > > user@debian:~/Desktop/src/Standards/susv4-2018$ grep -rn "pointer to a > function" > functions/regfree.html:530:"undefined" means that the action > by the application is an error, of similar severity to passing a bad > pointer to a function.</p> > functions/dlsym.html:138:<p>Note that conversion from a <b>void *</b> > pointer to a function pointer as in:</p> > functions/regcomp.html:530:"undefined" means that the action > by the application is an error, of similar severity to passing a bad > pointer to a function.</p> > functions/regexec.html:530:"undefined" means that the action > by the application is an error, of similar severity to passing a bad > pointer to a function.</p> > functions/V2_chap02.html:3039:<p>There are three types of action that > can be associated with a signal: SIG_DFL, SIG_IGN, or a pointer to a > function. Initially, > functions/regerror.html:530:"undefined" means that the action > by the application is an error, of similar severity to passing a bad > pointer to a function.</p> > user@debian:~/Desktop/src/Standards/susv4-2018$ grep -rn "function pointer" > basedefs/glob.h.html:165:"../functions/glob.html"><i>glob</i>()</a> > prototype definition by removing the <b>restrict</b> qualifier from the > function pointer > xrat/V4_xsh_chap02.html:114:when the application requires it; for > example, if its address is to be stored in a function pointer variable.</p> > functions/dlsym.html:138:<p>Note that conversion from a <b>void *</b> > pointer to a function pointer as in:</p> > user@debian:~/Desktop/src/Standards/susv4-2018$ grep -rn "pointer to > function" > functions/dlsym.html:73:converted from type pointer to function to type > pointer to <b>void</b>; otherwise, <i>dlsym</i>() shall return the > address of the > user@debian:~/Desktop/src/Standards/susv4-2018$ > > From those, the only one that documents this is functions/dlsym. > The rest is noise. > > The most explicit paragraph in dlsym is the following: > > [[ > Note that conversion from a void * pointer to a function pointer as in: > > fptr = (int (*)(int))dlsym(handle, "my_function"); > > is not defined by the ISO C standard. > This standard requires this conversion to work correctly > on conforming implementations. > ]] Okay -- so, one more thing for a revised (squashed) patch. I think you better say that that POSIX requirements exists only since POS0X.1-2008 Technical Corrigendum 1 (2013). Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
