Remove arbitrary [-1024,1024] limit in cross_compute_int()

Copy the algorithm used by autoconf.

It computes the upper and lower limits by starting at [-1,1] and
multiply by 2 at each iteration. This is even faster for small numbers
(the common case), for example it finds value 0 in just 2 compilations
where old algorithm would check for 1024, 512, ..., 0.

5 files changed, 65 insertions, 18 deletions

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 56b46b4..27cf43a 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -367,24 +367,52 @@ class CCompiler(Compiler):
         return self.compiles(t.format(**fargs), env, extra_args, dependencies)
 
     def cross_compute_int(self, expression, low, high, guess, prefix, env, extra_args, dependencies):
+        # Try user's guess first
         if isinstance(guess, int):
             if self._compile_int('%s == %d' % (expression, guess), prefix, env, extra_args, dependencies):
                 return guess
 
-        cur = low
-        while low < high:
-            cur = int((low + high) / 2)
-            if cur == low:
-                break
-
-            if self._compile_int('%s >= %d' % (expression, cur), prefix, env, extra_args, dependencies):
-                low = cur
+        # If no bounds are given, compute them in the limit of int32
+        maxint = 0x7fffffff
+        minint = -0x80000000
+        if not isinstance(low, int) or not isinstance(high, int):
+            if self._compile_int('%s >= 0' % (expression), prefix, env, extra_args, dependencies):
+                low = cur = 0
+                while self._compile_int('%s > %d' % (expression, cur), prefix, env, extra_args, dependencies):
+                    low = cur + 1
+                    if low > maxint:
+                        raise EnvironmentException('Cross-compile check overflowed')
+                    cur = cur * 2 + 1
+                    if cur > maxint:
+                        cur = maxint
+                high = cur
             else:
+                low = cur = -1
+                while self._compile_int('%s < %d' % (expression, cur), prefix, env, extra_args, dependencies):
+                    high = cur - 1
+                    if high < minint:
+                        raise EnvironmentException('Cross-compile check overflowed')
+                    cur = cur * 2
+                    if cur < minint:
+                        cur = minint
+                low = cur
+        else:
+            # Sanity check limits given by user
+            if high < low:
+                raise EnvironmentException('high limit smaller than low limit')
+            condition = '%s <= %d && %s >= %d' % (expression, high, expression, low)
+            if not self._compile_int(condition, prefix, env, extra_args, dependencies):
+                raise EnvironmentException('Value out of given range')
+
+        # Binary search
+        while low != high:
+            cur = low + int((high - low) / 2)
+            if self._compile_int('%s <= %d' % (expression, cur), prefix, env, extra_args, dependencies):
                 high = cur
+            else:
+                low = cur + 1
 
-        if self._compile_int('%s == %d' % (expression, cur), prefix, env, extra_args, dependencies):
-            return cur
-        raise EnvironmentException('Cross-compile check overflowed')
+        return low
 
     def compute_int(self, expression, low, high, guess, prefix, env, extra_args=None, dependencies=None):
         if extra_args is None:
@@ -416,7 +444,7 @@ class CCompiler(Compiler):
         }}'''
         if not self.compiles(t.format(**fargs), env, extra_args, dependencies):
             return -1
-        return self.cross_compute_int('sizeof(%s)' % typename, 1, 1024, None, prefix, env, extra_args, dependencies)
+        return self.cross_compute_int('sizeof(%s)' % typename, None, None, None, prefix, env, extra_args, dependencies)
 
     def sizeof(self, typename, prefix, env, extra_args=None, dependencies=None):
         if extra_args is None:
@@ -454,7 +482,7 @@ class CCompiler(Compiler):
             char c;
             {type} target;
         }};'''
-        return self.cross_compute_int('offsetof(struct tmp, target)', 1, 1024, None, t.format(**fargs), env, extra_args, dependencies)
+        return self.cross_compute_int('offsetof(struct tmp, target)', None, None, None, t.format(**fargs), env, extra_args, dependencies)
 
     def alignment(self, typename, prefix, env, extra_args=None, dependencies=None):
         if extra_args is None:
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index b04d586..6e3b864 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -984,20 +984,20 @@ class CompilerHolder(InterpreterObject):
         check_stringlist(args)
         expression = args[0]
         prefix = kwargs.get('prefix', '')
-        l = kwargs.get('low', -1024)
-        h = kwargs.get('high', 1024)
+        low = kwargs.get('low', None)
+        high = kwargs.get('high', None)
         guess = kwargs.get('guess', None)
         if not isinstance(prefix, str):
             raise InterpreterException('Prefix argument of compute_int must be a string.')
-        if not isinstance(l, int):
+        if low is not None and not isinstance(low, int):
             raise InterpreterException('Low argument of compute_int must be an int.')
-        if not isinstance(h, int):
+        if high is not None and not isinstance(high, int):
             raise InterpreterException('High argument of compute_int must be an int.')
         if guess is not None and not isinstance(guess, int):
             raise InterpreterException('Guess argument of compute_int must be an int.')
         extra_args = self.determine_args(kwargs)
         deps = self.determine_dependencies(kwargs)
-        res = self.compiler.compute_int(expression, l, h, guess, prefix, self.environment, extra_args, deps)
+        res = self.compiler.compute_int(expression, low, high, guess, prefix, self.environment, extra_args, deps)
         mlog.log('Computing int of "%s": %d' % (expression, res))
         return res
 
diff --git a/test cases/common/142 compute int/config.h.in b/test cases/common/142 compute int/config.h.in
index ad8d077..0de63ab 100644
--- a/test cases/common/142 compute int/config.h.in
+++ b/test cases/common/142 compute int/config.h.in
@@ -1,2 +1,4 @@
 #define INTSIZE @INTSIZE@
 #define FOOBAR_IN_CONFIG_H @FOOBAR@
+#define MAXINT @MAXINT@
+#define MININT @MININT@
diff --git a/test cases/common/142 compute int/meson.build b/test cases/common/142 compute int/meson.build
index 43553fe..22bd266 100644
--- a/test cases/common/142 compute int/meson.build
+++ b/test cases/common/142 compute int/meson.build
@@ -7,11 +7,15 @@ cc = meson.get_compiler('c')
 
 intsize = cc.compute_int('sizeof(int)', low : 1, high : 16, guess : 4)
 foobar = cc.compute_int('FOOBAR_IN_FOOBAR_H', prefix : '#include "foobar.h"', include_directories : inc)
+maxint = cc.compute_int('INT_MAX', prefix: '#include <limits.h>')
+minint = cc.compute_int('INT_MIN', prefix: '#include <limits.h>')
 
 cd = configuration_data()
 cd.set('INTSIZE', intsize)
 cd.set('FOOBAR', foobar)
 cd.set('CONFIG', 'config.h')
+cd.set('MAXINT', maxint)
+cd.set('MININT', minint)
 configure_file(input : 'config.h.in', output : 'config.h', configuration : cd)
 s = configure_file(input : 'prog.c.in', output : 'prog.c', configuration : cd)
 
@@ -23,11 +27,15 @@ cpp = meson.get_compiler('cpp')
 
 intsize = cpp.compute_int('sizeof(int)')
 foobar = cpp.compute_int('FOOBAR_IN_FOOBAR_H', prefix : '#include "foobar.h"', include_directories : inc)
+maxint = cpp.compute_int('INT_MAX', prefix: '#include <limits.h>')
+minint = cpp.compute_int('INT_MIN', prefix: '#include <limits.h>')
 
 cdpp = configuration_data()
 cdpp.set('INTSIZE', intsize)
 cdpp.set('FOOBAR', foobar)
 cdpp.set('CONFIG', 'config.hpp')
+cdpp.set('MAXINT', maxint)
+cdpp.set('MININT', minint)
 configure_file(input : 'config.h.in', output : 'config.hpp', configuration : cdpp)
 spp = configure_file(input : 'prog.c.in', output : 'prog.cc', configuration : cdpp)
 
diff --git a/test cases/common/142 compute int/prog.c.in b/test cases/common/142 compute int/prog.c.in
index 3ff1463..ff1ad55 100644
--- a/test cases/common/142 compute int/prog.c.in
+++ b/test cases/common/142 compute int/prog.c.in
@@ -1,6 +1,7 @@
 #include "@CONFIG@"
 #include <stdio.h>
 #include <wchar.h>
+#include <limits.h>
 #include "foobar.h"
 
 int main(int argc, char **argv) {
@@ -12,5 +13,13 @@ int main(int argc, char **argv) {
         fprintf(stderr, "Mismatch: computed int %d, should be %d.\n", FOOBAR_IN_CONFIG_H, FOOBAR_IN_FOOBAR_H);
         return 1;
     }
+    if(MAXINT != INT_MAX) {
+        fprintf(stderr, "Mismatch: computed max int %d, should be %d.\n", MAXINT, INT_MAX);
+        return 1;
+    }
+    if(MININT != INT_MIN) {
+        fprintf(stderr, "Mismatch: computed min int %d, should be %d.\n", MININT, INT_MIN);
+        return 1;
+    }
     return 0;
 }