Compilation prerequisites

General rules

If the traces are intended to be used for source coverage analysis, regardless of the actual criteria to be assessed afterwards, sources must be compiled with -g -fpreserve-control-flow -fdump-scos to control optimizations and allow mapping trace info to source constructs. -gno-strict-dwarf is required in addition for VxWorks targets, together with -mlongcall for PowerPC configurations.

Optimization is supported up to -O1, with inlining allowed. However, if the binary version of the code under test during the coverage campaign is intended to be used directly in operational conditions, care is needed to prevent inlining of the code under test within the testing code at compilation time in unit-testing campaigns. With GCC based toolchains such as GNAT Pro, this can be achieved by adding -fno-inline to the compilation options of the testing code.

The -fprofile-arcs or --coverage compilation switches, intended for analysis with the gcov tool, are incompatible with the needs of GNATcoverage for binary traces and must not be used. Likewise for the -gnatV family of GNAT Pro switches requesting data validity checks other than those mandated by the Ada RM (special case of -gnatVd).

For object coverage assessments, only -g is of possible use, if you intend to produce annotated sources as coverage reports. If source coverage analysis is to be performed as well, and you have no particular constraint on the form of the machine code for which object coverage is needed, the whole process might turn simpler if the same compilation options are used for both kinds of analysis. There is no incompatibility with object coverage analysis incurred by compiling the code compiled with options required for source coverage.

Consolidation related rules

For object or source level criteria, gnatcov computes the coverage achieved for the full set of routines or source units declared to be of interest amongst those exposed by the union of the exercised executables, as designated by the set of consolidated traces;

For the purpose of computing combined coverage achievements, two symbols are considered overlapping when all the following conditions are met:

• Both symbols have identical names at the object level,

• Both symbols have DWARF debug information attached to them,

• According to this debug information, both symbols originate from the same compilation unit, denoted by the full path of the corresponding source file.

By this construction, a symbol missing debug information is never considered overlapping with any other symbol. Whatever coverage is achieved on such a symbol never gets combined with anything else and the only kind of report where the symbol coverage is exposed is the =asm assembly output for object level criteria.

Moreover, for object level coverage criteria, gnatcov coverage will issue a consolidation error when two symbols are found to overlap but have structurally different machine code, which happens for example when the same unit is compiled with different different optimization levels for different executables.