https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93306
Bug ID: 93306
Summary: Unnecessary file I/O done for #if 0 &&
__has_include(...)
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: minor
Priority: P3
Component: preprocessor
Assignee: nathan at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
Given:
#if 0 && __has_include("foo.h")
#endif
strace shows a lot of redundant I/O:
stat("foo.h.gch", 0x7ffdc491f760) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "foo.h", O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file or
directory)
lstat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/home/jwakely", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib", {st_mode=S_IFDIR|0775, st_size=4096, ...}) =
0
lstat("/home/jwakely/gcc/10/lib/gcc", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/c++", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1", {st_mode=S_IFDIR|0775,
st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1/foo.h", 0x7ffdc491e620) = -1
ENOENT (No such file or directory)
stat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/../../../../include/c++/10.0.1/foo.h.gch",
0x7ffdc491f760) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD,
"/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/../../../../include/c++/10.0.1/foo.h",
O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file or directory)
lstat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/home/jwakely", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib", {st_mode=S_IFDIR|0775, st_size=4096, ...}) =
0
lstat("/home/jwakely/gcc/10/lib/gcc", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/c++", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1", {st_mode=S_IFDIR|0775,
st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1/x86_64-pc-linux-gnu",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1/x86_64-pc-linux-gnu/foo.h",
0x7ffdc491e620) = -1 ENOENT (No such file or directory)
stat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/../../../../include/c++/10.0.1/x86_64-pc-linux-gnu/foo.h.gch",
0x7ffdc491f760) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD,
"/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/../../../../include/c++/10.0.1/x86_64-pc-linux-gnu/foo.h",
O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file or directory)
lstat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/home/jwakely", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib", {st_mode=S_IFDIR|0775, st_size=4096, ...}) =
0
lstat("/home/jwakely/gcc/10/lib/gcc", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/c++", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1", {st_mode=S_IFDIR|0775,
st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1/backward",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include/c++/10.0.1/backward/foo.h", 0x7ffdc491e620)
= -1 ENOENT (No such file or directory)
stat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/../../../../include/c++/10.0.1/backward/foo.h.gch",
0x7ffdc491f760) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD,
"/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/../../../../include/c++/10.0.1/backward/foo.h",
O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file or directory)
lstat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/home/jwakely", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib", {st_mode=S_IFDIR|0775, st_size=4096, ...}) =
0
lstat("/home/jwakely/gcc/10/lib/gcc", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include/foo.h",
0x7ffdc491e620) = -1 ENOENT (No such file or directory)
stat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include/foo.h.gch",
0x7ffdc491f760) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD,
"/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include/foo.h",
O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file or directory)
lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/local/include", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/local/include/foo.h", 0x7ffdc491e620) = -1 ENOENT (No such file or
directory)
stat("/usr/local/include/foo.h.gch", 0x7ffdc491f760) = -1 ENOENT (No such file
or directory)
openat(AT_FDCWD, "/usr/local/include/foo.h", O_RDONLY|O_NOCTTY) = -1 ENOENT (No
such file or directory)
lstat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/home/jwakely", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/include", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/include/foo.h", 0x7ffdc491e620) = -1 ENOENT (No
such file or directory)
stat("/home/jwakely/gcc/10/include/foo.h.gch", 0x7ffdc491f760) = -1 ENOENT (No
such file or directory)
openat(AT_FDCWD, "/home/jwakely/gcc/10/include/foo.h", O_RDONLY|O_NOCTTY) = -1
ENOENT (No such file or directory)
lstat("/home", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/home/jwakely", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib", {st_mode=S_IFDIR|0775, st_size=4096, ...}) =
0
lstat("/home/jwakely/gcc/10/lib/gcc", {st_mode=S_IFDIR|0775, st_size=4096,
...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include-fixed",
{st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
lstat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include-fixed/foo.h",
0x7ffdc491e620) = -1 ENOENT (No such file or directory)
stat("/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include-fixed/foo.h.gch",
0x7ffdc491f760) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD,
"/home/jwakely/gcc/10/lib/gcc/x86_64-pc-linux-gnu/10.0.1/include-fixed/foo.h",
O_RDONLY|O_NOCTTY) = -1 ENOENT (No such file or directory)
lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/include", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
lstat("/usr/include/foo.h", 0x7ffdc491e620) = -1 ENOENT (No such file or
directory)
stat("/usr/include/foo.h.gch", 0x7ffdc491f760) = -1 ENOENT (No such file or
directory)
openat(AT_FDCWD, "/usr/include/foo.h", O_RDONLY|O_NOCTTY) = -1 ENOENT (No such
file or directory)
This affects uses like:
#if __cplusplus >= 201703L && __has_include(<optional>)
On IRC Nathan said "I see what's happening the __has_include evaluator is
ignoring the skip_eval counter"
