* [musl] Problem with strdupa in C++ code
@ 2022-04-12 1:06 Wolf
2022-04-12 16:15 ` Markus Wichmann
0 siblings, 1 reply; 3+ messages in thread
From: Wolf @ 2022-04-12 1:06 UTC (permalink / raw)
To: musl
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Hello,
I'm trying to compile C++ project in Alpine (so with musl) and I'm
hitting following error:
In file included from /usr/include/fortify/string.h:22,
from src/main/tools/linux-sandbox-pid1.cc:34:
src/main/tools/linux-sandbox-pid1.cc: In function 'int CreateTarget(const char*, bool)':
src/main/tools/linux-sandbox-pid1.cc:149:28: error: invalid conversion from 'void*' to 'char*' [-fpermissive]
149 | if (CreateTarget(dirname(strdupa(path)), true) < 0) {
| ^
| |
| void*
In file included from /usr/include/fortify/string.h:22,
from src/main/tools/linux-sandbox-pid1.cc:34:
/usr/include/string.h:31:15: note: initializing argument 1 of 'char* strcpy(char*, const char*)'
31 | char *strcpy (char *__restrict, const char *__restrict);
| ^~~~~~~~~~~~~~~~
If my reading for musl's code is correct, this is actually a bug in the
header file, since the declarations are:
void *alloca(size_t);
#define strdupa(x) strcpy(alloca(strlen(x)+1),x)
As far as I know, there is no automatic conversion from void* to char*
in C++. Should this be fixed by turning the define into
#define strdupa(x) strcpy((char*)alloca(strlen(x)+1),x)
? I think that should be both valid C and C++.
Best regards,
Tomas Volf
--
There are only two hard things in Computer Science:
cache invalidation, naming things and off-by-one errors.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [musl] Problem with strdupa in C++ code
2022-04-12 1:06 [musl] Problem with strdupa in C++ code Wolf
@ 2022-04-12 16:15 ` Markus Wichmann
2022-04-12 16:24 ` Joakim Sindholt
0 siblings, 1 reply; 3+ messages in thread
From: Markus Wichmann @ 2022-04-12 16:15 UTC (permalink / raw)
To: musl
Hi all,
so I tried to find some authority on this, but per the manpage,
strdupa() is a GNU extension. So I looked up the implementation in
glibc, which is near enough the only authority on whether this is
supposed to work in C++, and they do add the casts necessary to make it
work. Although they massively overcomplicate the matter with a statement
expression for God knows what reason.
So I guess we should add the cast, too. I see nothing obviously wrong
with the suggested replacement.
Ciao,
Markus
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [musl] Problem with strdupa in C++ code
2022-04-12 16:15 ` Markus Wichmann
@ 2022-04-12 16:24 ` Joakim Sindholt
0 siblings, 0 replies; 3+ messages in thread
From: Joakim Sindholt @ 2022-04-12 16:24 UTC (permalink / raw)
To: musl
On Tue, 12 Apr 2022 18:15:59 +0200, Markus Wichmann <nullplan@gmx.net> wrote:
> Although they massively overcomplicate the matter with a statement
> expression for God knows what reason.
To avoid referencing the argument twice, so you can strdupa(s++).
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-04-12 16:24 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-04-12 1:06 [musl] Problem with strdupa in C++ code Wolf
2022-04-12 16:15 ` Markus Wichmann
2022-04-12 16:24 ` Joakim Sindholt
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