https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110558
Bug ID: 110558
Summary: __has_include argument expansion results in unexpected
filename
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
Assignee: unassigned at gcc dot gnu.org
Reporter: provisorisch at online dot de
Target Milestone: ---
Hello!
I am building a path to an include file using a function like macro and then
checking if the file exists using __has_include.
However, if the argument to that macro is padded with spaces it will fail to
find the file.
Here an example with following 2 files in the same directory:
my.header.h:
--------
#pragma message("included my.header.h")
--------
test.c:
--------
#ifndef USE_IMPL
# define USE_IMPL my
#endif
#define STRINGIFY_(X) #X
#define STRINGIFY(X) STRINGIFY_(X)
#define MAKE_INCLUDE_PATH_(IMPL, NAME) STRINGIFY(IMPL.NAME)
#define MAKE_INCLUDE_PATH(NAME) MAKE_INCLUDE_PATH_(USE_IMPL, NAME)
// checking __has_include with spaces
#if __has_include(MAKE_INCLUDE_PATH( header.h )) // this will return false!
# pragma message("\""MAKE_INCLUDE_PATH( header.h )"\" exists")
#else
# pragma message("\""MAKE_INCLUDE_PATH( header.h )"\" does NOT exist!") //
except it does
#endif
#include MAKE_INCLUDE_PATH( header.h ) // works nonetheless
// checking __has_include without spaces
#if __has_include(MAKE_INCLUDE_PATH(header.h)) // works
# pragma message("\""MAKE_INCLUDE_PATH(header.h)"\" exists")
#else
# pragma message("\""MAKE_INCLUDE_PATH(header.h)"\" does NOT exist!")
#endif
#include MAKE_INCLUDE_PATH(header.h)
int main() { return 0; }
--------
Then to compile:
# gcc -Wall -Wextra test.c
test.c:14:12: note: ‘#pragma message: "my.header.h" does NOT exist!’
14 | # pragma message("\""MAKE_INCLUDE_PATH( header.h )"\" does NOT
exist!") // except it does
| ^~~~~~~
In file included from test.c:16:
my.header.h:1:9: note: ‘#pragma message: included my.header.h’
1 | #pragma message("included my.header.h")
| ^~~~~~~
test.c:20:12: note: ‘#pragma message: "my.header.h" exists’
20 | # pragma message("\""MAKE_INCLUDE_PATH(header.h)"\" exists")
| ^~~~~~~
In file included from test.c:24:
my.header.h:1:9: note: ‘#pragma message: included my.header.h’
1 | #pragma message("included my.header.h")
| ^~~~~~~
The first __has_include fails to find "my.header.h" but the subsequent #include
works.
The second __has_include works as expected.
Using strace I noticed that an extra space character ended up in the filename:
openat(AT_FDCWD, "my. header.h", O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file
or directory)
I would have expected the first __has_include to behave like the second one.
