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Add mechanism for creating project-specific aliases for built-in checks

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Specifically, the desired aliases can be specified as key-value pairs in
the autoconf.aliases map with key being the new name and the value --
old/existing. See the README for details.
This commit is contained in:
Boris Kolpackov 2022-09-07 09:28:00 +02:00
parent 3a324ad757
commit 367c4529d2
4 changed files with 268 additions and 90 deletions
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116
README.md
View File

@ -76,8 +76,8 @@ h{config}: in{config}
}
```
As key-value pairs in the `autoconf.substitutions` map (which is an alias for
the `in.substitutions` variable; see the [`in`][module-in] module for
Or as key-value pairs in the `autoconf.substitutions` map (which is an alias
for the `in.substitutions` variable; see the [`in`][module-in] module for
details):
```
@ -113,10 +113,74 @@ h{config}: in{config}
}
```
Note that an implementation of a check may depend on another check. As a
result, substitutions should not be conditional at the preprocessor level
(unless all the checks are part of the same condition). Nor should the
results of checks be adjusted until after the last check. For example:
While this module provides widely used aliases for some checks, it doesn't
attempt to cover every project's idiosyncrasies. Instead, it provides a
mechanism for creating project-specific aliases for built-in
checks. Specifically, the desired aliases can be specified as key-value pairs
in the `autoconf.aliases` map with key being the new name and the value --
old/existing. For example:
```
/* config.h.in */
#undef HAVE_AF_UNIX_H
#undef MY_SSIZE_T
```
```
h{config}: in{config}
{
autoconf.aliases = HAVE_AF_UNIX_H@HAVE_AFUNIX_H
autoconf.aliases += MY_SSIZE_T@ssize_t
}
```
The built-in checks can be prefixed in order to avoid clashes with similarly
named macros in other headers. This is an especially good idea if the
resulting header is public. To enable this, we specify the prefix with
the `autoconf.prefix` variable and then use the prefixed versions of
the options in the `config.h.in` file. For example:
```
/* config.h.in */
#undef LIBFOO_HAVE_STRLCPY
#undef LIBFOO_HAVE_STRLCAT
```
```
h{config}: in{config}
{
autoconf.prefix = LIBFOO_
}
```
Note that `autoconf.prefix` only affects the lookup of the built-in checks.
Custom substitutions and overrides of built-in checks must include the
prefix. Similarly, both names in `autoconf.aliases` must be specified
with the prefix (unless unprefixable; see below). For example:
```
h{config}: in{config}
{
autoconf.prefix = LIBFOO_
LIBFOO_HAVE_STRLCPY = true
autoconf.aliases = LIBFOO_SSIZE_T@ssize_t
}
```
Note also that some built-in check names are *unprefixable*, usually because
they are standard macro names (for example, `BYTE_ORDER`) that on some
platforms come from system headers (for example, `<sys/endian.h>` on FreeBSD).
Such checks have `!` after their names on the first line of their
implementation files (for example, `// BYTE_ORDER!`).
An implementation of a check may depend on another check. As a result,
substitutions should not be conditional at the preprocessor level (unless all
the checks are part of the same condition). Nor should the results of checks
be adjusted until after the last check. For example:
```
#ifndef _WIN32
@ -152,46 +216,6 @@ Below is the correct way to achieve the above semantics:
#endif
```
The built-in checks can be prefixed in order to avoid clashes with similarly
named macros in other headers. This is an especially good idea if the
resulting header is public. To enable this, we specify the prefix with
the `autoconf.prefix` variable and then use the prefixed versions of
the options in the `config.h.in` file. For example:
```
/* config.h.in */
#undef LIBFOO_HAVE_STRLCPY
#undef LIBFOO_HAVE_STRLCAT
```
```
h{config}: in{config}
{
autoconf.prefix = LIBFOO_
}
```
Note that `autoconf.prefix` only affects the lookup of the built-in checks.
Custom substitutions and overrides of built-in checks must include the
prefix. For example:
```
h{config}: in{config}
{
autoconf.prefix = LIBFOO_
LIBFOO_HAVE_STRLCPY = true
}
```
Note also that some built-in check names are *unprefixable*, usually because
they are standard macro names (for example, `BYTE_ORDER`) that on some
platforms come from system headers (for example, `<sys/endian.h>` on FreeBSD).
Such checks have `!` after their names on the first line of their
implementation files (for example, `// BYTE_ORDER!`).
## Adding new checks
To add a check for a new configuration option `<NAME>` simply create the

74
libbuild2-autoconf-tests/module/testscript
View File

@ -424,3 +424,77 @@ cat config.h >>EOO
#define _POSIX_SOURCE 1
#define FOO 1
EOO
: alias-map
:
mkdir build;
ln -s ../../bootstrap.build ../../root.build build/;
cat <<EOI >=config.h.in;
#undef TEST_DUMMY1_H
#undef TEST_DUMMY2_H
#undef TEST_DUMMY3_H
EOI
$* <<EOI &config.h &config.h.d;
./: h{config}: in{config}
{
autoconf.aliases = TEST_DUMMY1_H@zzz_TEST_DUMMY1_H
autoconf.aliases += TEST_DUMMY2_H@zzz_TEST_DUMMY2_H
autoconf.aliases += TEST_DUMMY3_H@zzz_TEST_DUMMY3_H
zzz_TEST_DUMMY2_H = '#define zzz_TEST_DUMMY2_H 20'
}
EOI
cat config.h >>EOO
#define zzz_TEST_DUMMY1_H 1
#undef TEST_DUMMY1_H
#ifdef zzz_TEST_DUMMY1_H
# define TEST_DUMMY1_H zzz_TEST_DUMMY1_H
#endif
#define zzz_TEST_DUMMY2_H 20
#undef TEST_DUMMY2_H
#ifdef zzz_TEST_DUMMY2_H
# define TEST_DUMMY2_H zzz_TEST_DUMMY2_H
#endif
#define zzz_TEST_DUMMY3_H 1
#undef TEST_DUMMY3_H
#define TEST_DUMMY3_H zzz_TEST_DUMMY3_H
EOO
: alias-map-prefix
:
mkdir build;
ln -s ../../bootstrap.build ../../root.build build/;
cat <<EOI >=config.h.in;
#undef PREFIX_TEST_DUMMY1_H
#undef PREFIX_TEST_DUMMY3_H
EOI
$* <<EOI &config.h &config.h.d;
./: h{config}: in{config}
{
autoconf.prefix = PREFIX_
autoconf.aliases = PREFIX_TEST_DUMMY1_H@PREFIX_zzz_TEST_DUMMY1_H
autoconf.aliases += PREFIX_TEST_DUMMY3_H@zzz_TEST_DUMMY3_H
}
EOI
cat config.h >>EOO
#define PREFIX_zzz_TEST_DUMMY1_H 1
#undef PREFIX_TEST_DUMMY1_H
#ifdef PREFIX_zzz_TEST_DUMMY1_H
# define PREFIX_TEST_DUMMY1_H PREFIX_zzz_TEST_DUMMY1_H
#endif
#define zzz_TEST_DUMMY3_H 1
#undef PREFIX_TEST_DUMMY3_H
#define PREFIX_TEST_DUMMY3_H zzz_TEST_DUMMY3_H
EOO

8
libbuild2-autoconf/libbuild2/autoconf/init.cxx
View File

@ -48,6 +48,14 @@ namespace build2
//
vp.insert_alias (*vp.find ("in.substitutions"),
"autoconf.substitutions");
// Alias map. The key is the new name and the value is the aliased
// (old) name.
//
// Note that this map is only consulted when resolving build-in checks
// and the names should include the prefix, if any.
//
vp.insert<map<string, string>> ("autoconf.aliases");
}
// Register the rule.

130
libbuild2-autoconf/libbuild2/autoconf/rule.cxx
View File

@ -19,6 +19,8 @@ namespace build2
{
enum class flavor {autoconf, cmake, meson};
using alias_map = map<string, string>;
// Wrap the in::rule's perform_update recipe into a data-carrying recipe.
//
// To optimize this a bit further we will call in::rule::perform_update()
@ -29,6 +31,7 @@ namespace build2
{
autoconf::flavor flavor;
string prefix;
const alias_map* aliases;
map<string, string> checks; // Checks already seen.
const autoconf::rule& rule;
@ -89,11 +92,12 @@ namespace build2
}
}
// Get the prefix if any.
// Get the prefix and aliases, if any.
//
string p (cast_empty<string> (t["autoconf.prefix"]));
const alias_map* a (cast_null<alias_map> (t["autoconf.aliases"]));
return match_data {f, move (p), {}, *this};
return match_data {f, move (p), a, {}, *this};
}
return r;
@ -502,10 +506,7 @@ namespace build2
// looking it up. So we store prefixless. Actually, it's convenient
// to store both.
//
// 2. Look in the catalog and fall through if not found.
//
// 3. If found, then check for a custom value falling through if
// found.
// 2. Check for a custom value falling through if found.
//
// Here things get a bit tricky: while a stray HAVE_* buildfile
// variable is unlikely, something like const or volatile is
@ -515,22 +516,29 @@ namespace build2
// While this clashes with the in.null semantics, it's just as
// easy to set the variable to the real default value as to null.
//
//
// 3. Look in the catalog and fall through if not found.
//
// 4. Return the build-in value from the catalog.
//
const char* pn (nullptr); // Prefixless name.
auto deprefix = [&md] (const string& n) -> const char*
{
const string& p (md.prefix);
if (!p.empty ())
{
// Note that if there is no prefix, then we only look for an
// unprefixable built-in check.
//
if (n.size () > p.size () && n.compare (0, p.size (), p) == 0)
pn = n.c_str () + p.size ();
return (n.size () > p.size () && n.compare (0, p.size (), p) == 0
? n.c_str () + p.size ()
: nullptr);
}
else
pn = n.c_str ();
return n.c_str ();
};
// Note that if there is no prefix in the name, then we only look for
// an unprefixable built-in check.
//
const char* pn (deprefix (n)); // Prefixless name.
const char* en (pn != nullptr ? pn : n.c_str ()); // Effective name.
// Note: this line must be recognizable by substitute_special().
@ -579,13 +587,11 @@ namespace build2
// Note: original name in the custom substitution lookup.
//
const check* c (find (en, pn == nullptr));
if (c != nullptr && !custom (n))
if (!custom (n))
{
// The plan is as follows: keep adding base checks (suppressing
// duplicates) followed by the main check while prefixing all the
// already seen names (unless unprefixable).
// The overall plan is as follows: add checks (to r; suppressing
// duplicates) while prefixing all the already seen names (in ns;
// unless unprefixable).
//
string r;
small_vector<string, 1> ns;
@ -605,10 +611,12 @@ namespace build2
r += v;
};
auto prefix = [&p, &ns, &r, b = size_t (0)] () mutable
auto prefix = [&md, &ns, &r, b = size_t (0)] () mutable
{
auto sep = [] (char c) { return !alnum (c) && c != '_'; };
const string& p (md.prefix);
for (const string& n: ns)
{
size_t m (n.size ()); // Prefix-less name length.
@ -627,7 +635,7 @@ namespace build2
b = r.size ();
};
// Base checks.
// Append base checks.
//
// @@ TODO: detect cycles (currently we just prune, like an
// include guard).
@ -640,16 +648,16 @@ namespace build2
//
auto base = [this,
&l, &t, a, smap, &null,
&md, &p, &ns,
&md, &ns,
&find, &custom,
&append, &prefix] (const string& n,
&append, &prefix] (const string& dn,
const char* bs,
const auto& base) -> void
{
auto df = make_diag_frame (
[&n] (const diag_record& dr)
[&dn] (const diag_record& dr)
{
dr << info << "while resolving base options for " << n;
dr << info << "while resolving base options for " << dn;
});
for (size_t b (0), e (0); next_word (bs, b, e); )
@ -686,7 +694,7 @@ namespace build2
//
bool up (strchr (c->modifier, '!') != nullptr);
string n ((up ? string () : p) + pn);
string n ((up ? string () : md.prefix) + pn);
md.checks.emplace (pn, n);
@ -701,7 +709,7 @@ namespace build2
append (c->value);
}
if (!p.empty ())
if (!md.prefix.empty ())
{
if (!up)
ns.push_back (move (pn));
@ -711,6 +719,69 @@ namespace build2
}
};
// Return true if the built-in check is prefix-compatible with the
// substitution.
//
auto prefix_compatible = [&md] (const check* c, const char* pn)
{
return (md.prefix.empty () || // No prefix.
strchr (c->modifier, '!') == nullptr || // Prefixable.
pn == nullptr); // Unprefixed.
};
// See if this is an alias.
//
if (md.aliases != nullptr)
{
auto i (md.aliases->find (n));
if (i != md.aliases->end ())
{
// Reduce this to the base with a synthesized "derived" check
// (pretty much how we would implement it if it were a built-in
// check).
//
const string& an (i->second);
pn = deprefix (an);
en = pn != nullptr ? pn : an.c_str ();
const check* c (find (en, pn == nullptr));
if (c == nullptr || !prefix_compatible (c, pn))
fail (l) << "unknown aliased option " << en <<
info << "while resolving alias " << n;
base (n, en, base);
// As a heuristics, for an unprefixable check we do a straight
// #define since it may not be a macro (see ssize_t).
//
// Note also that all the names are already prefixed, if
// necessary.
//
if (strchr (c->modifier, '!') != nullptr)
{
append (("#undef " + n + '\n' +
"#define " + n + ' ' + an + '\n').c_str ());
}
else
{
append (("#undef " + n + '\n' +
"#ifdef " + an + '\n' +
"# define " + n + ' ' + an + '\n' +
"#endif\n").c_str ());
}
return r;
}
}
const check* c (find (en, pn == nullptr));
if (c != nullptr && prefix_compatible (c, pn))
{
// The plan is as follows: keep adding base checks (suppressing
// duplicates) followed by the main check while prefixing all the
// already seen names (unless unprefixable).
//
if (*c->base != '\0')
base (n, c->base, base);
@ -718,7 +789,7 @@ namespace build2
//
append (c->value);
if (!p.empty ())
if (!md.prefix.empty ())
{
if (pn != nullptr) // Not unprefixable.
ns.push_back (pn);
@ -729,6 +800,7 @@ namespace build2
return r;
}
}
}
return in::rule::lookup (l, a, t, n, nullopt, smap, null);
}