9. Configuration Pragmas

Configuration pragmas include those pragmas described as such in the Ada Reference Manual, as well as implementation-dependent pragmas that are configuration pragmas. See section `Implementation Defined Pragmas' in GNAT Reference Manual, for details on these additional GNAT-specific configuration pragmas. Most notably, the pragma Source_File_Name, which allows specifying non-default names for source files, is a configuration pragma. The following is a complete list of configuration pragmas recognized by GNAT:

Ada_83 Ada_95 Ada_05 Ada_2005 Ada_12 Ada_2012 Annotate Assertion_Policy Assume_No_Invalid_Values C_Pass_By_Copy Check_Name Check_Policy Compile_Time_Error Compile_Time_Warning Compiler_Unit Component_Alignment Convention_Identifier Debug_Policy Detect_Blocking Default_Storage_Pool Discard_Names Elaboration_Checks Eliminate Extend_System Extensions_Allowed External_Name_Casing Fast_Math Favor_Top_Level Float_Representation Implicit_Packing Initialize_Scalars Interrupt_State License Locking_Policy Long_Float No_Run_Time No_Strict_Aliasing Normalize_Scalars Optimize_Alignment Persistent_BSS Polling Priority_Specific_Dispatching Profile Profile_Warnings Propagate_Exceptions Queuing_Policy Ravenscar Restricted_Run_Time Restrictions Restrictions_Warnings Reviewable Short_Circuit_And_Or Source_File_Name Source_File_Name_Project Style_Checks Suppress Suppress_Exception_Locations Task_Dispatching_Policy Universal_Data Unsuppress Use_VADS_Size Validity_Checks Warnings Wide_Character_Encoding

9.1 Handling of Configuration Pragmas
9.2 The Configuration Pragmas Files

9.1 Handling of Configuration Pragmas

Configuration pragmas may either appear at the start of a compilation unit, or they can appear in a configuration pragma file to apply to all compilations performed in a given compilation environment.

GNAT also provides the gnatchop utility to provide an automatic way to handle configuration pragmas following the semantics for compilations (that is, files with multiple units), described in the RM. See 8.2 Operating gnatchop in Compilation Mode for details. However, for most purposes, it will be more convenient to edit the `gnat.adc' file that contains configuration pragmas directly, as described in the following section.

In the case of Restrictions pragmas appearing as configuration pragmas in individual compilation units, the exact handling depends on the type of restriction.

Restrictions that require partition-wide consistency (like No_Tasking) are recognized wherever they appear and can be freely inherited, e.g. from a with'ed unit to the with'ing unit. This makes sense since the binder will in any case insist on seeing consistent use, so any unit not conforming to any restrictions that are anywhere in the partition will be rejected, and you might as well find that out at compile time rather than at bind time.

For restrictions that do not require partition-wide consistency, e.g. SPARK or No_Implementation_Attributes, in general the restriction applies only to the unit in which the pragma appears, and not to any other units.

The exception is No_Elaboration_Code which always applies to the entire object file from a compilation, i.e. to the body, spec, and all subunits. This restriction can be specified in a configuration pragma file, or it can be on the body and/or the spec (in eithe case it applies to all the relevant units). It can appear on a subunit only if it has previously appeared in the body of spec.

9.2 The Configuration Pragmas Files

In GNAT a compilation environment is defined by the current directory at the time that a compile command is given. This current directory is searched for a file whose name is `gnat.adc'. If this file is present, it is expected to contain one or more configuration pragmas that will be applied to the current compilation. However, if the switch `-gnatA' is used, `gnat.adc' is not considered.

Configuration pragmas may be entered into the `gnat.adc' file either by running gnatchop on a source file that consists only of configuration pragmas, or more conveniently by direct editing of the `gnat.adc' file, which is a standard format source file.

In addition to `gnat.adc', additional files containing configuration pragmas may be applied to the current compilation using the switch `-gnatec'path. path must designate an existing file that contains only configuration pragmas. These configuration pragmas are in addition to those found in `gnat.adc' (provided `gnat.adc' is present and switch `-gnatA' is not used).

It is allowed to specify several switches `-gnatec', all of which will be taken into account.

If you are using project file, a separate mechanism is provided using project attributes, see 12.1.3 Specifying Configuration Pragmas for more details.